Metals and Non-metals: Class 10 Science · Chapter 3

Science · Companion notes, simulations and practice · Official NCERT chapter PDF ↗

Published 12 Oct 2026 · Updated 12 Oct 2026

105 min
35 practice questions
24 MCQs

What you will learn in Metals and Non-metals

Compare metals and non-metals by lustre, hardness, malleability, ductility, conduction and sonority, and name the important exceptions
Classify oxides as basic, acidic or amphoteric and write balanced equations for metals reacting with oxygen, water and dilute acids
Build the reactivity series from experimental evidence and use it to predict displacement reactions
Show the formation of ionic compounds by electron transfer with electron-dot structures and explain their properties
Describe how metals are concentrated, extracted and refined according to their place in the reactivity series
Explain the conditions for rusting and how corrosion is prevented by coatings, galvanising and alloying

Original companion text aligned to NCERT Science Class 10, Chapter 3, pp. 37–57. Not affiliated with or endorsed by NCERT.

Look around a kitchen. The pressure cooker is aluminium or steel, the tap is often brass, and the gas stove has copper and steel parts. Now think of the coal in an angithi, the sulphur in a box of matches and the oxygen we breathe. They behave nothing like those utensils. In Class 9 you met elements as the simplest pure substances. Chemists sort most of them into two large families: metals (धातु) and non-metals (अधातु).

This chapter asks what makes a metal a metal. We test physical properties first, then see how metals react with oxygen, water, acids and each other's salts. Those results line up into the reactivity series. The series then explains why metals form ions, how they are won from rocks and purified, and why iron rusts while gold keeps its shine for centuries.

3.1 Physical Properties

The quickest way to tell materials apart is to look at them, tap them, bend them, and check whether heat or electricity passes through them. None of these tests changes what the substance is made of, so they reveal its physical properties.

3.1.1 Metals

Pick up a new steel spoon, a copper wire and a sheet of aluminium foil. All three shine, feel cool to the touch, and bend instead of snapping. Let us test such features one at a time, using samples of iron, copper, aluminium, magnesium, zinc and lead (Fig. 3.1).

5/5Lustre, malleability, ductility and sonority are typical of metals.

Fig. 3.1Four quick tests for a metal.

A two-by-two grid of small scenes. Step 1 highlights the top-left scene: sandpaper rubs a dull metal strip and leaves a bright, shiny patch, labelled lustre. Step 2 highlights the top-right scene: a hammer has flattened a lump of metal on an iron block into a wide thin sheet, labelled malleable. Step 3 highlights the bottom-left scene: a thick rod is pulled through a hole in a steel plate and comes out as a long thin wire, labelled ductile. Step 4 highlights the bottom-right scene: a metal bell is struck and sound waves spread out, labelled sonorous. Step 5 shows all four scenes together.

Activity 3.1NCERT Activity 3.1 · p. 37

Where does the shine come from?

You’ll need

a tarnished copper wire
an old iron nail
a strip of aluminium
a piece of magnesium ribbon
a sheet of sandpaper

Predict first

What will you see where you rub the dull copper wire with sandpaper?

The same dull brown colourA bright, shiny surfaceBlack powder all the way through

Look at each sample in good light and note how its surface looks.
Rub a small patch of each sample with sandpaper until it changes.
Compare the rubbed patch with the rest of the surface.

Sweet shops decorate kaju katli with varq, silver beaten so thin that it tears like tissue paper. The property of being hammered or rolled into thin sheets without cracking is called malleability (आघातवर्ध्यता). Gold and silver top the list of malleable metals.

Definition

Malleable

Able to be beaten or rolled into thin sheets without breaking.

ExampleAluminium foil for packing rotis; silver varq on sweets.

A metal that can be stretched into fine wire is ductile, and this property is its ductility (तन्यता). No metal is more ductile than gold: a single gram of it can be drawn into a wire more than a kilometre long. Malleability and ductility together let us shape metals into sheets, rods, vessels and wires to suit each use.

Definition

Ductile

Able to be drawn out into thin wires.

ExampleCopper for electric wiring; steel for guitar strings.

Most cooking vessels are made of aluminium, steel or copper, while their handles are often wood or plastic. Why use a metal for the pan but not for the handle? Activity 3.5 checks how well a metal carries heat.

Activity 3.5NCERT Activity 3.5 · p. 38

Pins that drop in turn

You’ll need

a copper or aluminium strip about 20 cm long
a stand with a clamp
three drawing pins
candle wax
a spirit lamp or a candle

Predict first

Which pin will fall first?

The pin nearest the flameThe pin farthest from the flameAll three at the same moment

Clamp one end of the strip so that the strip sticks out sideways.
Using drops of molten wax, stick three pins under the strip at 5 cm, 10 cm and 15 cm from its free end.
Heat the free end in the flame and watch the pins.
Note whether the strip itself melts.

Strip the end of an electric wire and you find bright copper or aluminium strands inside a jacket of PVC plastic. The strands carry the current; the jacket is there so that the current cannot pass into a person who touches the wire. Activity 3.6 builds a simple tester to check whether a solid conducts electricity.

1/3Copper closes the gap: the bulb glows.

Fig. 3.2A simple conduction tester.NCERT Fig. 3.2 · p. 39

Two cells, a bulb and wires form a loop with a gap at the bottom, where a sample is held between two crocodile clips. In step 1 the sample is a copper key and the bulb glows, with arrows showing current flowing round the loop. In step 2 the sample is a yellow lump of sulphur and the bulb stays dark, labelled no current. In step 3 the sample is a pencil lead made of graphite and the bulb glows again, showing that this non-metal conducts.

Drop a steel spoon and a wooden spoon on the floor. The steel one rings; the wooden one thuds. Metals that produce a ringing sound when struck are sonorous. That is why school bells, temple bells, ghungroo and cymbals are made of metal.

3.1.2 Non-metals

Only a small share of the elements are non-metals, but they matter enormously: the oxygen and nitrogen of air, the carbon in every living thing, the chlorine in bleach, the iodine in iodised salt, the sulphur on a matchstick head. At room temperature most of them are gases or brittle solids; red-brown bromine is the lone liquid. Do they pass the tests that metals pass? Try them.

Activity 3.7NCERT Activity 3.7 · p. 39

Put non-metals through the same tests

You’ll need

a piece of charcoal or coal
a pencil lead (graphite)
a lump of sulphur
the metal samples from the earlier activities
the conduction tester from Activity 3.6

Repeat the shine, cutting, hammer and wire tests of Activities 3.1 to 3.4 on each non-metal.
Clip each sample into the conduction tester.
Record every result in the table, together with your results for three metals.

Table 3.1Metals and non-metals side by side

Sample	Shiny?	Hard?	Flattens?	Conducts?	Rings?
Copper
Aluminium
Iron
Charcoal
Sulphur
Pencil lead

Your entries are saved automatically.

Your table shows clear trends, but Table 3.2 shows that every trend has exceptions. So physical properties alone cannot sort all the elements.

Table 3.2Rules and their exceptions

Usual rule	Exception
Metals are solids at room temperature	Mercury is a liquid
Metals melt only at high temperatures	Gallium and caesium melt on a warm palm
Metals are hard	Lithium, sodium and potassium cut like butter; they are also light and melt easily
Non-metals are dull	Iodine crystals have a metallic lustre
Non-metals are soft or brittle	Diamond, a form of carbon, is harder than any other natural material, and melts and boils only at very high temperatures
Non-metals do not conduct	Graphite, another form of carbon, conducts electricity

Diamond and graphite are both pure carbon. Different forms of the same element, with their atoms arranged differently, are called allotropes. The arrangement changes the properties completely: one is the hardest substance in nature, the other is soft enough to write with.

Compare

Metals and non-metals: physical properties

Metals

Lustrous
Usually hard; malleable and ductile
Good conductors of heat and electricity
Sonorous
Solids, except mercury

Non-metals

Mostly dull (iodine shines)
Brittle as solids; neither malleable nor ductile
Poor conductors (graphite conducts electricity)
Not sonorous
Solids or gases; bromine is a liquid

Because the physical rules leak, chemists rely more on chemical behaviour to classify an element. A good first test is to burn the element and find out what kind of oxide it makes.

Activity 3.8NCERT Activity 3.8 · p. 40

What kind of oxide?

You’ll need

a 3 cm strip of magnesium ribbon
a little sulphur powder in a deflagrating spoon
tongs and a burner
a test tube, a watch-glass and water
red and blue litmus paper

Predict first

The white ash from burning magnesium is mixed with water. What will it do to red litmus?

Turn it blueLeave it redBleach it white

Hold the magnesium ribbon in the flame with tongs and collect the white ash on a watch-glass.
Mix the ash with a few drops of water and touch it with red and then blue litmus paper.
Heat the sulphur until it catches fire, and hold an upside-down test tube over it to trap the gas.
Pour a little water into the test tube, shake it, and test the liquid with both litmus papers.
Write equations for both burnings.

4/4The gas in water turns blue litmus red: an acidic oxide.

Fig. 3.3A metal oxide and a non-metal oxide behave in opposite ways.NCERT Activity 3.8 · p. 40

Two columns. Step 1 shows magnesium ribbon held in tongs burning with a bright star of light and leaving white ash. Step 2 adds, below it, the ash mixed with water in a dish, with a strip of red litmus that has turned blue, labelled basic. Step 3 shows, in the right column, sulphur burning in a spoon with an upside-down test tube collecting the gas. Step 4 adds, below it, the test tube with water and a strip of blue litmus that has turned red, labelled acidic.

Magnesium burns

2 M g + O_{2} \overset{}{\to} 2 M g O

(3.1)

A basic solution

\begin{aligned} M g O + H_{2} O \\ \overset{}{\to} M g (O H)_{2} \end{aligned}

(3.2)

Sulphur burns

S + O_{2} \overset{}{\to} S O_{2}

(3.3)

An acidic solution

\begin{aligned} S O_{2} + H_{2} O \\ \overset{}{\to} H_{2} S O_{3} \end{aligned}

(3.4)

where

$H_{2} S O_{3}$: sulphurous acid

Practice · 2 questions

Practice: physical properties (NCERT in-text questions, p. 40): questions with answers

1
Short answerEasyNCERT in-text Questions p. 40, Q1
Name a metal that fits each description.
1. It would pour out of a bottle on a cool morning.
  Show solution
  AnswerMercury
  Mercury is the only metal that is liquid at room temperature.
2. A teacher can slice it with a table knife.
  Show solution
  AnswerSodium (or potassium, lithium)
  The alkali metals lithium, sodium and potassium are soft enough to cut with a knife.
3. It would make the quickest-heating pan if cost did not matter.
  Show solution
  AnswerSilver
  Silver conducts heat best of all metals, with copper close behind.
4. It conducts heat poorly compared with most metals.
  Show solution
  AnswerLead (or mercury)
  Among metals, lead and mercury carry heat relatively badly.
Short answerEasyNCERT in-text Questions p. 40, Q2
A goldsmith hammers one gold bead into a leaf so thin that light shows through it, and draws another bead into a fine wire for an earring. Name the property of gold used in each case and say what it means.
Show solution
AnswerMalleability for the leaf; ductility for the wire.
The leaf uses malleability: a malleable metal can be hammered or rolled into thin sheets without cracking.
The wire uses ductility: a ductile metal can be stretched or drawn into thin wires. Gold is the most malleable and the most ductile of all metals.

3.2 Chemical Properties of Metals

In this section you watch metals react with oxygen, water, dilute acids and solutions of other metals' salts. Keep a set of samples ready: aluminium, copper, iron, lead, magnesium and zinc, plus sodium for the teacher's demonstrations. Watch how fast each one reacts, because the speed tells you how reactive the metal is.

3.2.1 What happens when Metals are burnt in Air?

Activity 3.9NCERT Activity 3.9 · p. 41

Which metals burn?

You’ll need

small pieces or powders of the sample metals
tongs and a burner
safety goggles

Your teacher holds each sample in the flame with tongs.
Note whether it burns, the colour of any flame, and how the surface looks once it has cooled.
Collect any product and check whether it dissolves in water.
Rank the metals by how readily they combine with oxygen.

Table 3.3Metals in a flame

Metal	Burns?	Flame colour	Product and its look
Magnesium
Aluminium
Zinc
Iron
Copper
Lead

Your entries are saved automatically.

Heat most metals in air and they take up oxygen, turning into a metal oxide:

\begin{aligned} metal + oxygen \\ ⟶ metal oxide \end{aligned}

(3.5)

A bright copper wire held in a flame comes out black, because a skin of copper(II) oxide has formed on it. Aluminium powder burns to give white aluminium oxide:

2 C u + O_{2} \overset{}{\to} 2 C u O

(3.6)

\begin{aligned} 4 A l + 3 O_{2} \\ \overset{}{\to} 2 A l_{2} O_{3} \end{aligned}

(3.7)

Chapter 2 treated metal oxides as bases, and most of them are: black copper(II) oxide, for instance, dissolves in dilute hydrochloric acid to give a blue-green salt solution. Aluminium oxide and zinc oxide are two-faced. In an acid they neutralise it like a base; in sodium hydroxide solution they neutralise that like an acid. Either way, a salt and water form. Oxides with this double behaviour are called amphoteric oxides (उभयधर्मी ऑक्साइड).

Definition

Amphoteric oxide

A metal oxide that reacts with both acids and bases to form a salt and water.

ExampleAluminium oxide, $A l_{2} O_{3}$ , and zinc oxide, $Z n O$ .

Acting as a base

\begin{aligned} A l_{2} O_{3} + 6 H C l \\ \overset{}{\to} 2 A l C l_{3} + 3 H_{2} O \end{aligned}

(3.8)

Acting as an acid

\begin{aligned} A l_{2} O_{3} + 2 N a O H \\ \overset{}{\to} 2 N a A l O_{2} + H_{2} O \end{aligned}

(3.9)

where

$N a A l O_{2}$: sodium aluminate, a salt

Example 3.1

Zinc oxide on both sides

Zinc oxide is the white powder in calamine lotion. Show that it is amphoteric by writing balanced equations for its reactions with dilute hydrochloric acid and with sodium hydroxide solution. The salt formed with the base is sodium zincate, $N a_{2} Z n O_{2}$ .

Try it yourself first. Then reveal the solution one step at a time.

Drop most metal oxides into water and they just sit there. Sodium oxide and potassium oxide behave differently: they dissolve and react, leaving a strongly alkaline solution (an alkali is a base that dissolves in water):

\begin{aligned} N a_{2} O + H_{2} O \\ \overset{}{\to} 2 N a O H \end{aligned}

(3.10)

Potassium oxide reacts in the same way to give potassium hydroxide, $K O H$ . Activity 3.9 also showed that metals react with oxygen at very different speeds, as summed up in Table 3.4.

Table 3.4How some metals behave with oxygen

Metal	With oxygen	So we…
Potassium, sodium	React so fast in open air that they can catch fire	store them under kerosene, away from air and moisture
Magnesium, aluminium, zinc, lead	Get a thin oxide skin at room temperature	rely on the skin: it shields the metal from further attack
Iron	A lump does not burn, but fine filings burn with sparks in a flame	enjoy the sparks of a phuljhadi (sparkler), made with iron filings
Copper	Does not burn; hot copper gets a black coat of $C u O$	clean the coat off with dilute acid
Silver, gold	Do not react, even when strongly heated	use them for jewellery and coins

So far, sodium is clearly the most reactive of our samples, and magnesium comes next. Burning cannot rank zinc, iron, copper and lead against one another, however. We need other tests.

3.2.2 What happens when Metals react with Water?

Activity 3.10NCERT Activity 3.10 · p. 42

Cold water, hot water, steam

You’ll need

small pieces of the sample metals
beakers of cold water and of hot water
for steam: a boiling tube with wet glass wool, a burner and a delivery tube

Your teacher drops a small piece of each metal into a beaker half-filled with cold water. Note which react, how violently, and whether any metal floats or catches fire.
Metals that show no change are tried in hot water.
Metals that still show no change are heated strongly in steam from the wet glass wool; any gas is led off and tested with a burning splint.
Rank the metals by how readily they react with water.

4/4Pb, Cu, Ag and Au show no reaction with water.

Fig. 3.4Metals sorted by the conditions they need to react with water.NCERT Fig. 3.3 · p. 43

A ladder of four rows, revealed one per step. Step 1, cold water: potassium, sodium and calcium, with a note that the reaction can be violent. Step 2, hot water: magnesium, which reacts slowly and floats. Step 3, steam: aluminium, zinc and iron, which give the oxide and hydrogen. Step 4, no reaction: lead, copper, silver and gold. An arrow down the side reads less reactive.

Water is a gentler attacker than oxygen, so it sorts the metals more finely. Whenever a metal does react with water, one product is hydrogen gas; the other is the metal oxide or, if that oxide dissolves, the metal hydroxide. Go down the ladder of Fig. 3.4 one rung at a time.

Cold water, violently: potassium and sodium. A small piece skates over the surface, hissing, and gives out so much heat that the hydrogen often bursts into flame:

Very violent; heat is released

\begin{aligned} 2 K + 2 H_{2} O \\ \overset{}{\to} 2 K O H + H_{2} \end{aligned}

(3.11)

Violent; heat is released

\begin{aligned} 2 N a + 2 H_{2} O \\ \overset{}{\to} 2 N a O H + H_{2} \end{aligned}

(3.12)

Cold water, gently: calcium. It fizzes steadily, but too little heat is given out to light the hydrogen. Soon the lump rises and floats, carried by the hydrogen bubbles clinging to it:

\begin{aligned} C a + 2 H_{2} O \\ \overset{}{\to} C a (O H)_{2} + H_{2} \end{aligned}

(3.13)

Hot water: magnesium. Cold water barely touches it. In hot water it slowly gives magnesium hydroxide and hydrogen, and it too ends up riding on its own bubbles:

With hot water

\begin{aligned} M g + 2 H_{2} O \\ \overset{}{\to} M g (O H)_{2} + H_{2} \end{aligned}

(3.14)

Steam only: aluminium, zinc and iron. Cold and hot water leave them alone, but the red-hot metal in steam gives the oxide and hydrogen:

\begin{aligned} 2 A l + 3 H_{2} O (g) \\ \overset{}{\to} A l_{2} O_{3} + 3 H_{2} \end{aligned}

(3.15)

\begin{aligned} Z n + H_{2} O (g) \\ \overset{}{\to} Z n O + H_{2} \end{aligned}

(3.16)

Example 3.2

Balancing iron with steam

Red-hot iron reacts with steam to give hydrogen and the black, magnetic oxide $F e_{3} O_{4}$ . Write the balanced equation.

Try it yourself first. Then reveal the solution one step at a time.

Water leaves lead, copper, silver and gold untouched, whether it is cold, hot or steam. That is one reason copper is a good choice for water pipes and tanks, and why silver and gold ornaments stay bright in rain.

3.2.3 What happens when Metals react with Acids?

Chapter 2 showed that dilute acids attack many metals, producing hydrogen gas and a salt:

\begin{aligned} metal + dilute acid \\ ⟶ salt + hydrogen \end{aligned}

(3.17)

Do all metals react with acids, and equally fast? Activity 3.11 finds out.

Activity 3.11NCERT Activity 3.11 · p. 44

A bubble race in dilute acid

You’ll need

clean pieces of magnesium, aluminium, zinc, iron and copper of about the same size
five test tubes holding equal volumes of dilute hydrochloric acid
a thermometer
sandpaper

Predict first

In which tube will the temperature rise the most?

The tube with copperThe tube with ironThe tube with magnesiumAll tubes equally

Rub each metal clean with sandpaper.
Note the starting temperature of the acid.
Drop one metal into each tube. Watch how fast bubbles form, and read the temperature in each tube after two minutes.
Rank the metals by how vigorously they react.

Table 3.5The bubble race

Metal	Bubbles (none, few, many)	Temperature rise (°C)
Magnesium
Aluminium
Zinc
Iron
Copper

Your entries are saved automatically.

3/3The bubbling ranks the metals: Mg > Al > Zn > Fe, and Cu does not react.

Fig. 3.5Bubbles of hydrogen show which metal reacts fastest.

Five test tubes of dilute hydrochloric acid stand in a rack, labelled magnesium, aluminium, zinc, iron and copper. In step 1 each tube has just received its piece of metal and nothing has happened yet. In step 2 bubbles of hydrogen rise: many from magnesium, fewer from aluminium and zinc, a few from iron and none from copper, and the magnesium tube is labelled warmest. Step 3 adds an arrow below the rack reading most reactive on the left to least reactive on the right.

Rank the tubes by fizz and by warmth and you get the same order: Mg > Al > Zn > Fe. The copper tube stays still and cool: dilute hydrochloric acid leaves copper untouched. For magnesium:

\begin{aligned} M g + 2 H C l \\ \overset{}{\to} M g C l_{2} + H_{2} \end{aligned}

(3.18)

Aluminium, zinc and iron give similar equations, forming aluminium chloride, zinc chloride and iron(II) chloride.

3.2.4 How do Metals react with Solutions of other Metal Salts?

Oxygen, water and acids could not rank every metal, because some metals do not react with them at all. A sharper test is to put one metal into a solution of another metal's salt and see whether they swap places.

Activity 3.12NCERT Activity 3.12 · p. 44

Zinc meets copper sulphate

You’ll need

a strip or granule of zinc
a few pieces of clean copper wire
copper(II) sulphate solution
zinc sulphate solution
two test tubes

Predict first

Which tube will show a change?

Zinc in copper(II) sulphateCopper in zinc sulphateBoth tubesNeither tube

Put the zinc into the copper(II) sulphate solution, and the copper into the zinc sulphate solution.
Leave both tubes for about 30 minutes.
Look at the metal surfaces and the colour of each solution. Decide in which tube a reaction took place, and how you can tell.
Write a balanced equation for any reaction and name its type.

3/3Each zinc atom gives two electrons to a copper ion: zinc is oxidised, copper ions are reduced.

Fig. 3.6A metal higher in the series pushes a lower one out of its salt solution.NCERT Fig. 3.4 · p. 45

Two beakers. The left beaker holds blue copper sulphate solution with a grey zinc strip; the right beaker holds colourless zinc sulphate solution with a copper strip. In step 1 nothing has happened yet. In step 2, thirty minutes later, the zinc strip is covered with a brown coat of copper and the blue solution has become pale, while the right beaker is unchanged and labelled no change. Step 3 adds the ionic equation: zinc atoms give two electrons to copper ions and become zinc ions.

Here is the general rule. A metal higher in reactivity can displace, that is take the place of, a lower one in a compound, whether the compound is dissolved in water or melted. Turned around, it becomes a test: whenever metal A pulls metal B out of a solution of B's salt, A is the more reactive of the two.

\begin{aligned} A + salt of B \\ ⟶ salt of A + B \end{aligned}

(3.19)

\begin{aligned} Z n + C u S O_{4} \\ \overset{}{\to} Z n S O_{4} + C u \end{aligned}

(3.20)

This is a displacement reaction, the type you met in Chapter 1. The same thing happens when an iron nail is left in copper(II) sulphate solution: the nail turns brown and the blue solution slowly becomes pale green iron(II) sulphate. So iron is more reactive than copper as well.

Example 3.3

Ranking metals from displacement results

Four metals W, X, Y and Z were placed, one at a time, in three salt solutions. The table shows what happened.

Table 3.6Results

Metal	Zinc sulphate	Lead nitrate	Silver nitrate
W	no change	displaced	displaced
X	no change	no change	no change
Y	displaced	displaced	displaced
Z	no change	no change	displaced

(a) Arrange W, X, Y and Z in order of decreasing reactivity. (b) Which of them could be copper?

Try it yourself first. Then reveal the solution one step at a time.

3.2.5 The Reactivity Series

Put all these results together, along with the displacement experiments of Chapter 1, and the common metals line up in a single list, from the most reactive at the top to the least reactive at the bottom. This list is the reactivity series (सक्रियता श्रेणी), also called the activity series (Fig. 3.7).

1/3The common metals in order of decreasing reactivity.

Fig. 3.7The reactivity series, with what it predicts.NCERT Table 3.2 · p. 45

Thirteen tiles step down a staircase from top left to bottom right: K, Na, Ca, Mg, Al, Zn, Fe, Pb, then H in square brackets with a dashed outline, then Cu, Hg, Ag and Au. The top is labelled most reactive and the bottom least reactive. Step 2 draws a line through hydrogen: the metals above it are marked as giving hydrogen with dilute acids and those below as not. Step 3 colours the tiles in four bands by how each metal is extracted: electrolysis for K to Al, reduction with carbon for Zn to Pb, heating alone for Cu and Hg, and found free for Ag and Au.

Hydrogen is not a metal, but it is placed in the series in square brackets, between lead and copper. Metals above it push hydrogen out of dilute acids; metals below it cannot. That is why copper, mercury, silver and gold give no hydrogen with dilute hydrochloric acid.

InteractiveDisplacement explorer

An interactive reactivity series. The learner picks one of eleven metals, from potassium to gold, and one of seven solutions: magnesium sulphate, zinc sulphate, iron(II) sulphate, lead nitrate, copper(II) sulphate, silver nitrate and dilute hydrochloric acid. A ladder of the series highlights the chosen metal and the metal (or hydrogen) in the solution. A panel then says whether a displacement happens, gives the balanced equation, and describes what you would see, such as a brown copper coat and a fading blue colour. Special cases are explained: potassium, sodium and calcium react with the water instead, aluminium starts slowly because of its oxide skin, and lead soon stops because an insoluble coat forms. A score counts the learner's correct predictions when the predict-first switch is on.

Fig. 3.8Pick a metal and a solution to predict whether a reaction happens, then read the equation and what you would see. The ladder shows where both metals sit in the reactivity series.

Practice · 5 questions

Practice: reactivity (NCERT in-text questions, p. 46): questions with answers

Short answerEasyNCERT in-text Questions p. 46, Q1
A chemicals shop keeps lumps of potassium in a bottle of paraffin oil. Why? What would happen if the bottle were left open in a humid room?
Show solution
AnswerThe oil keeps air and moisture away; without it potassium would oxidise and could catch fire.
Potassium reacts very fast with oxygen and violently with water, releasing enough heat to set fire to the hydrogen formed. Paraffin oil does not react with it and keeps air and moisture away.
In an open bottle in humid air the oil would not protect the exposed metal, which would tarnish quickly and could catch fire on contact with water.
2
Short answerMediumNCERT in-text Questions p. 46, Q2
Write balanced equations for these reactions.
1. Zinc heated in steam
  Show solution
  $Z n + H_{2} O (g)$ $\overset{}{\to} Z n O + H_{2}$
2. Magnesium with hot water
  Show solution
  $M g + 2 H_{2} O$ $\overset{}{\to} M g (O H)_{2} + H_{2}$
3. Sodium with cold water
  Show solution
  $2 N a + 2 H_{2} O$ $\overset{}{\to} 2 N a O H + H_{2}$
3
Short answerMediumNCERT in-text Questions p. 46, Q3
Four metals P, Q, R and S were added, one at a time, to solutions of zinc sulphate, iron(II) sulphate, copper(II) sulphate and silver nitrate. P displaced iron, copper and silver; Q displaced only silver; R displaced all four metals; S displaced copper and silver.
1. Which of the four metals sits highest in the reactivity series?
  Show solution
  AnswerR
  R displaces zinc, iron, copper and silver, so it is above all of them.
2. What would you see if S were added to copper(II) sulphate solution?
  Show solution
  AnswerA brown copper coat on S, and the blue colour fading
  The table shows that S displaces copper, so copper would deposit on S as a reddish-brown coat and the blue copper ions would be used up.
3. (c)
  Arrange P, Q, R and S in decreasing order of reactivity.
  R
  S
  P
  Q
  Show answer
  Answer
  R
  P
  S
  Q
  R displaces all four; P all but zinc; S only copper and silver; Q only silver.
Short answerEasyNCERT in-text Questions p. 46, Q4
Which gas is given off when a reactive metal is dropped into dilute sulphuric acid, and how would you test for it? Write the balanced equation for zinc with dilute sulphuric acid.
Show solution
AnswerHydrogen; it burns with a pop.
The gas is hydrogen. A burning splint held at the mouth of the tube makes it burn with a 'pop'.
For zinc: $Z n + H_{2} S O_{4}$ $\overset{}{\to} Z n S O_{4} + H_{2}$
Short answerMediumNCERT in-text Questions p. 46, Q5
What would you see if a strip of magnesium were placed in pale green iron(II) sulphate solution? Write the equation.
Show solution
AnswerA dark iron deposit on the magnesium; the green colour fades.
Magnesium is above iron, so it displaces iron. A dark grey or black layer of iron forms on the strip and the pale green colour fades as colourless magnesium sulphate forms.
The equation: $M g + F e S O_{4}$ $\overset{}{\to} M g S O_{4} + F e$

3.3 How do Metals and Non-metals React?

Why do metals react at all, and why do some react far more eagerly than others? Recall from Class 9 that the noble gases (helium, neon, argon …) hardly react. Their outermost shell is full: two electrons for helium and eight for the others. Other elements react in ways that give them such a full outer shell. Table 3.7 lists the shells of a few metals and non-metals.

Table 3.7Electrons in the shells of some elements

Element	Atomic number	K	L	M	N
		Electrons in shell
Neon (noble gas)	10	2	8	–	–
Argon (noble gas)	18	2	8	8	–
Sodium (metal)	11	2	8	1	–
Magnesium (metal)	12	2	8	2	–
Potassium (metal)	19	2	8	8	1
Calcium (metal)	20	2	8	8	2
Oxygen (non-metal)	8	2	6	–	–
Fluorine (non-metal)	9	2	7	–	–
Sulphur (non-metal)	16	2	8	6	–
Chlorine (non-metal)	17	2	8	7	–

Sodium is 2, 8, 1: a single electron sits alone in its third shell. Let that electron go, and the shell beneath, already holding a complete eight, becomes the outside of the particle. Now count charges: 11 protons in the nucleus but only 10 electrons. One positive charge is left over, so the particle is a positive ion, the sodium cation:

\underset{2, 8, 1}{N a} ⟶ \underset{2, 8}{N a^{+}} + e^{-}

(3.21)

Chlorine, 2, 8, 7, is in the opposite position: its outer shell lacks just one electron to hold eight. Once it gains that electron, its 17 protons face 18 electrons, leaving one spare negative charge. It is now the chloride anion:

\underset{2, 8, 7}{C l} + e^{-} ⟶ \underset{2, 8, 8}{C l^{-}}

(3.22)

Put the two together and each solves the other's problem: the electron sodium can spare is the one chlorine is missing (Fig. 3.9). The ions that result carry opposite charges and pull on each other strongly, and this electrostatic pull holds sodium chloride together. A grain of salt is therefore not a heap of separate 'NaCl molecules'. It is a vast, orderly stack of $N a^{+}$ and $C l^{-}$ ions, each gripped by its neighbours.

3/3Both now have a full outer shell: $N a^{+}$ and $C l^{-}$ attract each other.

Fig. 3.9Sodium chloride forms by the transfer of one electron.NCERT Fig. 3.5 · p. 47

Electron-dot diagrams. Step 1: a sodium atom with one outer electron drawn as a cross, labelled 2, 8, 1, and a chlorine atom with seven outer electrons drawn as dots, labelled 2, 8, 7. Step 2: the cross moves from sodium along a curved arrow and fills the gap on the chlorine atom. Step 3: an arrow leads to the products: a sodium ion in square brackets with a plus charge, labelled 2, 8, and a chloride ion in brackets with eight outer electrons and a minus charge, labelled 2, 8, 8; the two ions attract each other.

In Fig. 3.9 only the outer-shell electrons are drawn, as dots or crosses round the symbol. Such a drawing is an electron-dot structure. Crosses mark the metal's electrons so that you can follow where they go.

Magnesium (2, 8, 2) has two electrons to give, but a chlorine atom can take only one. So one magnesium atom reacts with two chlorine atoms (Fig. 3.10). Magnesium chloride, $M g C l_{2}$ , is made of $M g^{2 +}$ cations and twice as many $C l^{-}$ anions.

\underset{2, 8, 2}{M g} ⟶ \underset{2, 8}{M g^{2 +}} + 2 e^{-}

(3.23)

3/3One $M g^{2 +}$ ion and two $C l^{-}$ ions make magnesium chloride.

Fig. 3.10One magnesium atom gives one electron to each of two chlorine atoms.NCERT Fig. 3.6 · p. 48

Electron-dot diagrams. Step 1: a magnesium atom with two outer electrons drawn as crosses, labelled 2, 8, 2, between two chlorine atoms that each have seven dots and a gap facing the magnesium. Step 2: curved arrows carry one cross to each chlorine atom. Step 3: an arrow leads down to the products: a magnesium ion in brackets with charge 2+, between two chloride ions in brackets, each with eight outer electrons and a minus charge; every ion now has a full outer shell.

Whenever a metal hands electrons over to a non-metal, the product is an ionic compound (आयनिक यौगिक), also known as an electrovalent compound.

Definition

Ionic (electrovalent) compound

A compound of positive and negative ions held together by electrostatic attraction, formed when a metal transfers electrons to a non-metal.

ExampleSodium chloride, magnesium chloride and calcium oxide.

Example 3.4

Potassium sulphide by electron transfer

Show how potassium (atomic number 19) and sulphur (atomic number 16) form potassium sulphide. Name the ions and write the formula.

Try it yourself first. Then reveal the solution one step at a time.

Oxides are drawn the same way (Fig. 3.11). Oxygen (2, 6) needs two electrons. A lithium atom (2, 1) can give only one, so two lithium atoms are needed and the formula is $L i_{2} O$ ; a calcium atom gives both its outer electrons, so calcium oxide is simply $C a O$ .

Fig. 3.11Two lithium atoms, or one calcium atom, supply the two electrons an oxygen atom needs.

Two rows of electron-dot diagrams. Top row: two lithium atoms, each with one outer electron drawn as a cross, send their electrons along curved arrows to an oxygen atom with six dots; the products are two lithium ions in brackets with a plus charge each and an oxide ion in brackets with eight outer electrons and a charge of 2 minus. Bottom row: one calcium atom with two crosses sends both electrons to an oxygen atom; the products are a calcium ion with charge 2 plus and an oxide ion with charge 2 minus.

Compare

Metals and non-metals: chemical behaviour

Metals

Form basic oxides (a few are amphoteric)
Lose electrons to form positive ions
Those above hydrogen give hydrogen with dilute acids
Often act as reducing agents (give electrons)

Non-metals

Form acidic or neutral oxides (CO is neutral)
Gain electrons to form negative ions
Do not give hydrogen with dilute acids
Combine with hydrogen to form hydrides such as $H_{2} S$ and $N H_{3}$

3.3.1 Properties of Ionic Compounds

Activity 3.13NCERT Activity 3.13 · p. 48

Testing some salts

You’ll need

common salt (sodium chloride)
potassium chloride
calcium chloride
a metal spatula and a burner
small beakers of water and of kerosene
the conduction tester from Activity 3.6, with two clean iron nails as electrodes

Predict first

In which liquid will common salt dissolve?

KeroseneWaterBothNeither

Note the state and appearance of each salt.
Heat a little of one salt on the spatula in the flame. Note any colour the flame takes and whether the salt melts. Repeat with the others.
Shake a pinch of each salt with water in one beaker and with kerosene in another.
Dip the two nail electrodes of the tester into each water solution, keeping them apart, and watch the bulb.

The ions explain every one of these observations:

Hard but brittle solids. Strong attractions between oppositely charged ions make the crystals hard. A sharp blow shifts one layer of ions against the next, like charges come face to face and repel, and the crystal shatters.
High melting and boiling points. To melt the crystal, the ions must be shaken loose from one another, and their strong attraction makes that very costly in energy (Table 3.8).
Soluble in water, not in kerosene or petrol. Water molecules can pull the ions apart; kerosene and petrol cannot.
Conduct electricity when molten or dissolved, but not as solids. A current needs charged particles that can move. In the solid the ions are locked in place; melting or dissolving sets them free to drift towards the oppositely charged electrodes (Fig. 3.12).

Table 3.8Ionic compounds melt and boil far higher than molecular substances

Substance	Type	Melts (°C)	Boils (°C)
Sodium chloride	ionic	801	1465
Potassium chloride	ionic	770	1420
Magnesium oxide	ionic	2852	3600
Water	molecular	0	100
Ethanol	molecular	−114	78
Naphthalene	molecular	80	218

3/3Dissolved ions are free to move too, so the solution conducts.

Fig. 3.12Ions must be free to move to carry a current.NCERT Fig. 3.8 · p. 48

A cell, a bulb and two electrodes, marked plus and minus, dip into a sample of an ionic compound drawn as plus and minus ions. In step 1 the sample is solid: the ions sit in a neat grid, cannot move, and the bulb is dark. In step 2 the sample is molten over a flame: the ions are jumbled and drift, positive ions to the negative electrode and negative ions to the positive one, and the bulb glows. In step 3 the compound is dissolved in water: the ions are spread out and moving, and the bulb glows.

Practice · 2 questions

Practice: ionic compounds (NCERT in-text questions, p. 49): questions with answers

1
DiagramMediumNCERT in-text Questions p. 49, Q1
Potassium has atomic number 19, fluorine 9 and calcium 20.
1. Draw the electron-dot structures of potassium, fluorine and calcium.
  Show solution
  K (2, 8, 8, 1) has one outer electron: K with one cross. F (2, 7) has seven: F with three pairs of dots and one single dot. Ca (2, 8, 8, 2) has two: Ca with two crosses.
2. Show the formation of potassium fluoride and calcium fluoride by the transfer of electrons.
  Show solution
  Potassium fluoride: potassium's single cross moves to the gap beside fluorine. You get [K]⁺ and [F]⁻, the fluoride ion holding eight outer electrons (seven dots and one cross). Formula $K F$ .
  Calcium fluoride: one fluorine atom can take only one electron, so calcium's two crosses go to two different fluorine atoms, just as in Fig. 3.10. You get [Ca]²⁺ and two [F]⁻ ions. Formula $C a F_{2}$ .
3. Name the ions present in each compound.
  Show solution
  AnswerKF: K⁺ and F⁻. CaF₂: Ca²⁺ and F⁻.
  Potassium fluoride contains $K^{+}$ and $F^{-}$ in the ratio 1 : 1. Calcium fluoride contains $C a^{2 +}$ and $F^{-}$ in the ratio 1 : 2.
Short answerMediumNCERT in-text Questions p. 49, Q2
Furnaces are lined with bricks of magnesium oxide. Explain, in terms of its particles, why magnesium oxide survives such high temperatures.
Show solution
AnswerStrong attraction between Mg²⁺ and O²⁻ ions needs huge energy to overcome.
Magnesium oxide is an ionic compound: a giant stack of $M g^{2 +}$ and $O^{2 -}$ ions held by strong electrostatic attraction. Melting means breaking up this regular stack, which needs a very large amount of energy. With doubly charged ions the attraction is especially strong, so magnesium oxide melts only at about 2850 °C.

3.4 Occurrence of Metals

The bauxite dug from the hills of Odisha, the haematite of Chhattisgarh and the zinc ore of Rajasthan all come from the Earth's crust, the main store of the metals we use. The sea is a second, smaller store, holding salts such as sodium chloride and magnesium chloride in solution. Any element or compound formed by nature in the crust is a mineral (खनिज). When a mineral is so rich in a metal that extracting the metal pays, it is called an ore (अयस्क).

Definition

Ore

A mineral from which a metal can be extracted profitably.

ExampleBauxite is the ore of aluminium; haematite, $F e_{2} O_{3}$ , is an ore of iron. Every ore is a mineral, but not every mineral is an ore.

3.4.1 Extraction of Metals

Where a metal sits in the reactivity series tells you how nature stores it (Table 3.9). Unreactive metals have lasted for millions of years without combining with anything; reactive ones joined up with other elements long ago. Oxides are especially common among ores, because oxygen is both reactive and plentiful.

Table 3.9How a metal's reactivity decides the way it is found

Part of the series	How the metals occur	Examples
Bottom (least reactive)	Often free (native), as the metal itself; copper and silver also as sulphide or oxide ores	gold, silver, platinum, copper
Middle	Combined; their ores are usually oxides, sulphides or carbonates	zinc, iron, lead
Top (most reactive)	Never free; always combined	potassium, sodium, calcium, magnesium, aluminium

Extraction follows the same three-way split: one approach for metals of low reactivity, one for the middle and one for the top (third step of Fig. 3.7). Getting a metal out of its ore and purifying it is called metallurgy (धातुकर्म). Fig. 3.13 shows the route an ore follows.

4/4Hg, Cu: heating the sulphide in air is enough. Every metal is then refined.

Fig. 3.13From ore to pure metal: the method depends on reactivity.NCERT Fig. 3.10 · p. 50

A flow chart. Step 1: an ore box leads to concentration, where gangue is removed. Step 2 highlights the left branch for the most reactive metals, such as sodium: electrolysis of the molten compound gives the metal. Step 3 highlights the middle branch for metals like zinc: a sulphide ore is roasted, or a carbonate ore calcined, to give the oxide, which is then reduced with carbon. Step 4 highlights the right branch for metals of low reactivity such as mercury: heating the sulphide in air is enough. All three branches end at the metal, which is then refined to give pure metal.

3.4.2 Enrichment of Ores

Before cooking, rice and dal are picked clean of small stones and husk. Ore needs the same treatment on a giant scale. Rock from a mine carries plenty of soil, sand and stone, called gangue (गैंग), which has to go before any metal is extracted. This clean-up is called concentration or enrichment of the ore. The trick is always to exploit some property, physical or chemical, in which the ore and the gangue differ.

For example, heavy ore particles can be washed free of lighter sand in a stream of water. A magnetic iron ore can be picked out of non-magnetic rock with a magnet. Sulphide ores are often separated by froth flotation: the ore particles cling to an oily froth and float off, while the gangue sinks.

3.4.3 Extracting Metals Low in the Activity Series

Near the bottom of the series, metals hold oxygen so feebly that heat alone can release them. Mercury comes from cinnabar, mercury(II) sulphide. Roast cinnabar in air and its sulphur leaves as sulphur dioxide, leaving mercury(II) oxide; keep heating and the oxide itself breaks up into mercury and oxygen:

\begin{aligned} 2 H g S + 3 O_{2} \\ \overset{h e a t}{\to} 2 H g O \\ + 2 S O_{2} \end{aligned}

(3.24)

\begin{aligned} 2 H g O \\ \overset{h e a t}{\to} 2 H g + O_{2} \end{aligned}

(3.25)

Copper glance, $C u_{2} S$ , yields copper in a similar way. Part of the sulphide is heated in air to copper(I) oxide, which then reacts with the rest of the sulphide:

\begin{aligned} 2 C u_{2} S + 3 O_{2} \\ \overset{h e a t}{\to} 2 C u_{2} O \\ + 2 S O_{2} \end{aligned}

(3.26)

\begin{aligned} 2 C u_{2} O + C u_{2} S \\ \overset{h e a t}{\to} 6 C u \\ + S O_{2} \end{aligned}

(3.27)

3.4.4 Extracting Metals in the Middle of the Activity Series

Zinc, iron, lead and copper sit in the middle of the series and are usually mined as sulphides or carbonates. Chemists would rather start from an oxide, which is far easier to reduce, so the first job is to convert the ore:

Roasting (भर्जन): heating a sulphide ore strongly in plenty of air.
Calcination (निस्तापन): heating a carbonate ore strongly in little or no air.

Roasting

\begin{aligned} 2 Z n S + 3 O_{2} \\ \overset{h e a t}{\to} 2 Z n O \\ + 2 S O_{2} \end{aligned}

(3.28)

Calcination

\begin{aligned} Z n C O_{3} \\ \overset{h e a t}{\to} Z n O + C O_{2} \end{aligned}

(3.29)

Next the oxide is heated with a reducing agent, most often carbon in the form of coke, which carries the oxygen away. Recall from Chapter 1 that removing oxygen is reduction. Every extraction of a metal from its compound is, at heart, a reduction.

\begin{aligned} Z n O + C \\ \overset{}{\to} Z n + C O \end{aligned}

(3.30)

Example 3.5

Lead from two different ores

Lead is mined mostly as galena, lead(II) sulphide ( $P b S$ ), and sometimes as cerussite, lead(II) carbonate ( $P b C O_{3}$ ). For each ore, name the step that turns it into lead(II) oxide and write its equation. Then show how lead is obtained from the oxide.

Try it yourself first. Then reveal the solution one step at a time.

Carbon is not the only oxygen thief. A metal high in the series, such as sodium, calcium or aluminium, can strip the oxygen from the oxide of a metal lower down. Heating manganese dioxide with powdered aluminium, for instance, gives manganese:

\begin{aligned} 3 M n O_{2} + 4 A l \\ \overset{}{\to} 3 M n + 2 A l_{2} O_{3} \\ + h e a t \end{aligned}

(3.31)

Here aluminium gains oxygen, so it is oxidised, while manganese dioxide loses oxygen and is reduced.

Reactions of this kind give out heat so fast that the freed metal comes out as a liquid. The best known is the thermit reaction of iron(III) oxide with aluminium, which supplies white-hot molten iron for welding rails and mending broken machine parts on the spot:

Thermit reaction

\begin{aligned} F e_{2} O_{3} + 2 A l \\ \overset{}{\to} 2 F e + A l_{2} O_{3} \\ + h e a t \end{aligned}

(3.32)

Chromium metal is made in the same way, by heating chromium(III) oxide with aluminium powder:

\begin{aligned} C r_{2} O_{3} + 2 A l \\ \overset{}{\to} 2 C r + A l_{2} O_{3} \\ + h e a t \end{aligned}

(3.33)

Example 3.6

Who is oxidised, who is reduced?

Look at the reaction in (3.33). (a) Which substance is oxidised and which is reduced? (b) Why can aluminium do this job? (c) Why does the chromium come out as a liquid?

Try it yourself first. Then reveal the solution one step at a time.

3.4.5 Extracting Metals towards the Top of the Activity Series

Try heating sodium oxide, magnesium oxide or aluminium oxide with carbon and nothing happens: these metals grip oxygen more tightly than carbon can. They are won instead by electrolytic reduction, in which an electric current, passed through the molten compound, does the reducing.

For sodium, magnesium and calcium the starting material is the molten chloride. As the current flows through the melt, the metal builds up on the cathode (the negative electrode) and chlorine gas escapes at the anode (the positive electrode). With molten sodium chloride:

At the cathode

N a^{+} + e^{-} \overset{}{\to} N a

(3.34)

At the anode

2 C l^{-} \overset{}{\to} C l_{2} + 2 e^{-}

(3.35)

At the cathode, sodium ions gain electrons, so they are reduced. Aluminium is obtained in the same way, by electrolysing aluminium oxide. The compound must be molten rather than dissolved in water: in a water solution, hydrogen from the water would be released at the cathode instead of sodium.

3.4.6 Refining of Metals

Copper for electric wiring must be extremely pure, because even small amounts of impurity raise its resistance. Metal straight from a furnace is not that pure, so it is refined. The most widely used method is electrolytic refining (विद्युत-अपघटनी परिष्करण), applied to copper, nickel, zinc, tin, silver, gold and others.

Take copper (Fig. 3.14). A thick slab of the impure metal is connected as the anode, a thin sheet of pure copper as the cathode, and both dip into acidified copper(II) sulphate solution. As current flows, copper atoms leave the anode as $C u^{2 +}$ ions, cross the solution, and settle on the cathode as fresh, pure metal:

At the anode

C u \overset{}{\to} C u^{2 +} + 2 e^{-}

(3.36)

At the cathode

C u^{2 +} + 2 e^{-} \overset{}{\to} C u

(3.37)

The impurities part company. Those that dissolve stay behind in the solution; those that do not, often including precious silver and gold, drop to the floor of the tank under the anode as anode mud.

Definition

Electrolytic refining

Purifying a metal by electrolysis, with the impure metal as the anode, a thin sheet of the pure metal as the cathode, and a solution of a salt of the metal as the electrolyte.

ExampleImpure copper is refined in acidified copper(II) sulphate solution.

3/3The anode shrinks, the cathode grows, and insoluble impurities collect as anode mud.

Fig. 3.14Electrolytic refining of copper.NCERT Fig. 3.12 · p. 52

A tank of blue acidified copper sulphate solution with a thin pure-copper cathode on the left, connected to the negative terminal of a power supply, and a thick impure-copper anode on the right, connected to the positive terminal. In step 1 nothing flows. In step 2 copper ions, labelled Cu 2 plus, move from the anode across the solution to the cathode. In step 3 the anode has become thinner, the cathode thicker, and a heap of anode mud lies on the floor of the tank under the anode.

Quick check

1 of 4

Match each starting material with the right treatment.

Tap an item on the left, then its match on the right.

Show answer

Answer

Gold nuggets : found free; just separate
Zinc blende, ZnS : roast, then reduce with carbon
Molten sodium chloride : electrolysis
Impure copper : electrolytic refining

Gold occurs native; a middle metal's sulphide is roasted then reduced with carbon; a top metal needs electrolysis of its melt; impure copper is purified as an anode.

Practice · 3 questions

Practice: occurrence and extraction (NCERT in-text questions, p. 53): questions with answers

1
Short answerEasyNCERT in-text Questions p. 53, Q1
A company finds two deposits containing aluminium compounds. One is bauxite rich in aluminium oxide. The other is a clay holding only a little aluminium that would cost more to extract than it is worth.
1. Which deposit is an ore, and which is only a mineral? Explain.
  Show solution
  AnswerBauxite is an ore; the clay is a mineral but not an ore.
  Both are minerals, because nature formed them in the Earth's crust. Only bauxite is an ore, since aluminium can be extracted from it profitably.
2. The bauxite is mixed with sand and red soil. What are these called, and why are they removed first?
  Show solution
  AnswerGangue; it would waste energy and contaminate the metal.
  The unwanted sand and soil are gangue. They are removed first (concentration) so that energy is not wasted on processing them and they do not end up as impurities in the metal.
Short answerEasyNCERT in-text Questions p. 53, Q2
Name two metals that a prospector might find as nuggets of the pure metal, and explain why they occur free.
Show solution
AnswerGold and platinum (also silver, copper).
Gold and platinum (and sometimes silver and copper) occur free. They are so unreactive that they have not combined with oxygen, sulphur or other elements over geological time.
Short answerEasyNCERT in-text Questions p. 53, Q3
At a smelter, zinc oxide is heated with coke and zinc metal is obtained. What type of chemical change happens to the zinc oxide, and what job does the coke do?
Show solution
AnswerReduction; coke is the reducing agent.
Zinc oxide loses its oxygen, so it is reduced: $Z n O + C$ $\overset{}{\to} Z n + C O$ . The coke (carbon) takes the oxygen and is itself oxidised to carbon monoxide; it acts as the reducing agent.

3.5 Corrosion

Leave a shiny metal in air long enough and its surface changes. You met three examples in Chapter 1 (Table 3.10). This slow eating away of a metal by the air, moisture or chemicals around it is called corrosion (संक्षारण).

Table 3.10Three familiar kinds of corrosion

Metal	What you see	What has formed	Caused by
Silver	Ornaments and plates turn black	silver sulphide	sulphur compounds in the air
Copper	The brown surface turns green, as on old domes and statues	basic copper carbonate	moist carbon dioxide in the air
Iron	A brown, flaky coating	rust, a hydrated iron(III) oxide	oxygen and water together

Rusting is the costliest kind: bridges, ships, cars and railway coaches lose iron to it every year. Activity 3.14 finds out what iron needs in order to rust.

Activity 3.14NCERT Activity 3.14 · p. 53

What does iron need to rust?

You’ll need

three clean iron nails
three small glass jars with lids
tap water
water that has been boiled and cooled
a little cooking oil
two or three silica-gel sachets (from a shoe box or a medicine bottle)

Predict first

In which jar will the nail rust?

B: in boiled water under oilC: in dry air with silica gelA: partly in tap waterAll three, equally

Jar A: stand a nail in a little tap water so that it is partly covered. Close the lid.
Jar B: cover a nail with water that was boiled to drive out dissolved air and then cooled. Pour a thin layer of oil on top to keep air out. Close the lid.
Jar C: put a nail in the dry jar with the silica-gel sachets, which soak up moisture. Close the lid.
Leave the jars for four or five days, then compare the nails.

3/3Iron rusts only when both oxygen (air) and water are present.

Fig. 3.15Rusting needs both air and water.NCERT Fig. 3.13 · p. 53

Three closed glass jars, A, B and C, each with an iron nail. Jar A has a little tap water around the lower part of the nail. Jar B is filled with boiled water under a thin layer of oil. Jar C is dry, with small silica-gel sachets on the floor. In step 1, on day 0, all three nails are clean and grey. In step 2, on day 5, the nail in jar A is covered with brown rust, while the nails in B and C are still clean. Step 3 labels what each jar provides: air and water in A, water only in B, air only in C.

So anything that keeps air or water away from iron slows down rusting.

3.5.1 Prevention of Corrosion

There are two ways to beat rust. One is a barrier that keeps air and water off the iron: paint, oil, grease, or a plating of chromium (chrome plating) or zinc (galvanising). The other is to change the iron itself by making an alloy. Anodising, which you met earlier, guards aluminium in a similar barrier-like way. Paint, oil and grease help only while the layer is unbroken.

Galvanisation (यशदलेपन) gives iron or steel a thin coat of zinc; corrugated roofing sheets, buckets and fence wire are usually galvanised. Here is the surprise: even where the zinc gets scratched through, the iron underneath does not rust. Zinc is more reactive than iron, so where both metals meet air and water, the zinc is attacked first and the iron is spared (Fig. 3.16).

Definition

Galvanisation

Protecting iron or steel from rusting by giving it a thin coat of zinc.

ExampleGalvanised iron (GI) roofing sheets and buckets.

4/4Tin is less reactive than iron, so the exposed iron rusts.

Fig. 3.16Zinc protects iron even through a scratch; tin does not.

Two cut-away views side by side: on the left iron with a zinc coating, on the right iron with a tin coating. In step 1 both coatings are whole. In step 2 a scratch cuts through each coating down to the iron, and a drop of water sits in each scratch. In step 3, on the zinc side, the zinc next to the scratch corrodes away while the iron below stays clean, labelled zinc corrodes first. In step 4, on the tin side, brown rust grows in the scratch and spreads under the tin, labelled iron rusts.

Tin-plated steel behaves the other way round. Tin is less reactive than iron, so it protects only while it is unbroken; through a scratch, the iron underneath rusts. Tin is still chosen for food cans because it is unreactive and harmless, whereas zinc would react with acidic foods.

Almost every iron object you see is really an alloy. Pure iron is too soft for most jobs and stretches easily when hot. A pinch of carbon, usually less than one percent, turns it into steel, which is hard and strong. Add chromium and nickel and you get stainless steel, tough and rust-proof: think of a steel thali or tiffin box.

Steel is one example of an alloy (मिश्रातु): a metal blended so evenly with other metals, or with a non-metal, that the mixture is the same all through (homogeneous). Alloys are made by melting the main metal, dissolving the other elements in the melt in measured amounts, and letting it cool and set. An alloy containing mercury has a special name: an amalgam.

Definition

Alloy

A uniform (homogeneous) mixture in which a metal is blended with other metals, or with a non-metal such as carbon.

ExampleBrass (copper and zinc); steel (iron and carbon).

Alloying changes properties in useful ways (Table 3.11). An alloy usually melts at a lower temperature, and conducts electricity less well, than the pure metals in it. So house wiring is pure copper; brass and bronze go into taps, statues and bells; and solder, which melts easily, joins electrical wires.

Table 3.11Some common alloys

Alloy	Made of	Useful because	Used for
Steel	iron + a little carbon	hard and strong	buildings, rails, tools
Stainless steel	iron + chromium + nickel	hard; does not rust	utensils, surgical tools
Brass	copper + zinc	golden; does not corrode easily	taps, lamps, musical instruments
Bronze	copper + tin	hard; resists corrosion; rings well	statues, bells, medals
Solder	lead + tin	low melting point	joining electrical wires
22-carat gold	gold + copper or silver	harder than pure gold	jewellery

Practice · 3 questions

Practice: corrosion and alloys (NCERT in-text questions, p. 55): questions with answers

Quick answerMediumNCERT in-text Questions p. 55, Q1
Powders of aluminium, iron and lead are each heated with calcium oxide, iron(III) oxide and lead(II) oxide. Pick every pair in which the metal takes the oxygen and frees the other metal.
$A l + C a O$ $A l + F e_{2} O_{3}$ $A l + P b O$ $F e + C a O$ $F e + P b O$ $P b + F e_{2} O_{3}$
Select all that apply
Show solution
Use the series Ca > Al > Fe > Pb. A metal reacts only with the oxide of a metal below it: Al with $F e_{2} O_{3}$ and with $P b O$ , and Fe with $P b O$ . No metal here is above calcium, so CaO is never reduced.
Short answerEasyNCERT in-text Questions p. 55, Q2
Name two metals that stay bright for centuries without corroding, and say why.
Show solution
AnswerGold and platinum.
Gold and platinum are so unreactive that air, water and the sulphur compounds in air do not attack them. (Silver is also unreactive but slowly blackens with sulphur compounds.)
Short answerEasyNCERT in-text Questions p. 55, Q3
Define an alloy in your own words. Which alloy would an electrician use to join wires, and what is it made of?
Show solution
AnswerA uniform blend of a metal with other elements; solder is lead + tin.
An alloy is a metal blended uniformly with other metals, or with a non-metal such as carbon, so that every part of it has the same make-up. Solder, made of lead and tin, melts easily and is used to join electrical wires.

Recap

Metals and Non-metals: key points and summary

Metals are lustrous, malleable, ductile, sonorous and good conductors of heat and electricity; all are solid at room temperature except mercury (Section 3.1.1).
Non-metals are usually dull, brittle and poor conductors, with exceptions: graphite conducts, iodine is lustrous, diamond is very hard and bromine is a liquid (Section 3.1.2).
Metals form basic oxides; non-metals form acidic or neutral oxides. $A l_{2} O_{3}$ and $Z n O$ react with both acids and bases: they are amphoteric (Section 3.2.1).
Metals differ in how readily they react with oxygen, water and dilute acids (Section 3.2.2, Section 3.2.3).
The reactivity series runs from potassium at the top, through sodium, calcium, magnesium, aluminium, zinc, iron, lead, [hydrogen], copper, mercury and silver, to gold at the bottom (Section 3.2.5).
Metals above hydrogen push it out of dilute acids, and a metal higher in the series takes the place of a lower one in its salt solution (Section 3.2.4).
Metals lose electrons to form positive ions and non-metals gain them to form negative ions; the ions make up ionic compounds (Section 3.3).
Non-metals cannot push hydrogen out of dilute acids, and they combine with hydrogen to form hydrides (Section 3.3).
Ionic compounds are hard, brittle solids with high melting points; they dissolve in water but not in kerosene, and conduct when molten or dissolved (Section 3.3.1).
Metals occur free or as compounds in minerals; an ore is a mineral from which a metal can be extracted profitably (Section 3.4).
Metallurgy: concentrate the ore, convert it to the oxide by roasting or calcination, reduce it by heating, with carbon or by electrolysis according to reactivity, then refine (Section 3.4.1).
Electrolytic refining uses the impure metal as anode and pure metal as cathode in a solution of the metal's salt (Section 3.4.6).
Corrosion is the slow attack of a metal by its surroundings; iron rusts only when air and water are both present (Section 3.5).
Barriers (paint, oil, grease, chromium or zinc coats) and alloying stop rusting; an alloy is a metal blended evenly with other metals or a non-metal (Section 3.5.1).

Practice · 20 questions

Practice questions with answers (NCERT “Exercises”)

1
Quick answerEasyNCERT Exercises Q1
Which of these pairs will give a displacement reaction? Pick all that apply.
Zinc in copper(II) sulphate solutionSilver in zinc sulphate solutionIron in magnesium chloride solutionLead in silver nitrate solution
Select all that apply
Show answer
Answer
(A) Zinc in copper(II) sulphate solution
(D) Lead in silver nitrate solution
Zinc is above copper and lead is above silver, so those two react. Silver is below zinc and iron is below magnesium, so those two do not.
2
Quick answerEasyNCERT Exercises Q2
Pick every method that would keep an iron tawa from rusting while it is stored through the monsoon.
Wiping it dry and rubbing on a thin film of oilPutting it away wet in a closed cupboardWrapping it in newspaper soaked in salt waterStoring it in a box with a silica-gel sachet
Select all that apply
Show answer
Answer
(A) Wiping it dry and rubbing on a thin film of oil
(D) Storing it in a box with a silica-gel sachet
Oil keeps out air and water, and silica gel keeps the air dry. Leaving it wet or wrapping it in salty paper speeds up rusting.
Quick answerMediumNCERT Exercises Q3
An element X burns in air to give a white solid that melts only above 2500 °C. The solid dissolves in water, and the solution turns red litmus blue. X is most likely
sulphurphosphoruscalciumcopper
Show answer
Answer (C) calcium
Calcium oxide is ionic (very high melting point) and reacts with water to give the alkali calcium hydroxide. Sulphur and phosphorus give acidic oxides; copper(II) oxide is black and insoluble.
Quick answerMediumNCERT Exercises Q4
Brass and copper cooking vessels used to be coated with tin (kalai) before sour dishes were cooked in them. Why tin rather than zinc?
Zinc is too heavy for a thin coatingZinc is more reactive, so sour food would attack itZinc cannot stick to copperZinc is less reactive, so it would not protect the vessel
Show answer
Answer (B) Zinc is more reactive, so sour food would attack it
Zinc is above tin in the series, so the acids in sour food would react with a zinc coating and dissolve zinc salts into the food. Tin is much less reactive and harmless.
5
Short answerMediumNCERT Exercises Q5
Your lab has only a hammer and an LED tester (a cell, an LED and wires).
1. Describe two tests you would use to sort unknown solid elements into metals and non-metals.
  Show solution
  AnswerHammer test and conduction test.
  Hammer test: strike the sample on a hard surface. A metal flattens (malleable) and may ring (sonorous); a non-metal such as sulphur or charcoal crumbles.
  Conduction test: clip the sample into the tester. If the LED lights, the sample conducts, as metals do; most non-metals do not.
2. How reliable are these tests? Name an element that would mislead each one.
  Show solution
  AnswerGraphite misleads the conduction test; soft alkali metals can mislead the hammer test.
  Both tests work for most samples but not all. Graphite is a non-metal that lights the LED. A metal such as zinc may crack when cold and needs several blows, and sodium is too soft and too reactive to test this way. Chemical tests, such as the nature of the oxide, settle doubtful cases.
Short answerMediumNCERT Exercises Q6
A white oxide dissolves in dilute hydrochloric acid and also in sodium hydroxide solution. What kind of oxide is it? Suggest two oxides it could be, and write one equation for each reaction of one of them.
Show solution
AnswerAmphoteric, e.g. ZnO or Al₂O₃.
An oxide that reacts with both acids and bases to give a salt and water is amphoteric. Zinc oxide and aluminium oxide are both white amphoteric oxides. For zinc oxide:
With the acid: $Z n O + 2 H C l$ $\overset{}{\to} Z n C l_{2} + H_{2} O$
With the alkali: $Z n O + 2 N a O H$ $\overset{}{\to} N a_{2} Z n O_{2} + H_{2} O$
Short answerEasyNCERT Exercises Q7
You have strips of copper, magnesium, silver and zinc, and some dilute sulphuric acid. Which strips will give hydrogen? Explain using the reactivity series.
Show solution
AnswerMagnesium and zinc will; copper and silver will not.
Magnesium and zinc are above hydrogen in the reactivity series, so they displace it from the acid: bubbles of hydrogen appear. Copper and silver are below hydrogen, so they cannot displace it and nothing happens.
8
Short answerMediumNCERT Exercises Q8
A refinery purifies silver by electrolysis.
1. What is used as the anode?
  Show solution
  AnswerA block of impure silver
  The impure silver is made the anode, so that it dissolves.
2. What is used as the cathode?
  Show solution
  AnswerA thin strip of pure silver
  Pure silver deposits on a thin strip of pure silver, the cathode.
3. What is the electrolyte?
  Show solution
  AnswerA solution of a silver salt, such as silver nitrate
  The electrolyte must carry silver ions, so a solution of a soluble silver salt such as silver nitrate is used.
4. Where will any gold in the impure silver end up?
  Show solution
  AnswerIn the anode mud
  Gold is less reactive than silver and does not dissolve, so it falls below the anode as anode mud.
9
Short answerMediumNCERT Exercises Q9
Ananya burns a little sulphur in a deflagrating spoon inside a gas jar, then lowers strips of litmus into the jar.
1. What happens to a strip of dry blue litmus paper?
  Show solution
  AnswerNo change
  Dry sulphur dioxide is not an acid by itself, so dry litmus does not change.
2. What happens to a strip of moist blue litmus paper?
  Show solution
  AnswerIt turns red
  On the moist paper the gas dissolves to form sulphurous acid, which turns blue litmus red.
3. Write balanced equations for the burning and for the gas dissolving in water.
  Show solution
  Burning: $S + O_{2} \overset{}{\to} S O_{2}$ .
  Dissolving: $S O_{2} + H_{2} O$ $\overset{}{\to} H_{2} S O_{3}$ .
10
Short answerEasyNCERT Exercises Q10
Suggest a suitable way to prevent rusting for each object.
1. A bicycle chain
  Show solution
  AnswerOiling or greasing
  Oil or grease keeps out air and water and also lets the links move freely; paint would crack off.
2. A corrugated iron roof
  Show solution
  AnswerGalvanising
  A zinc coating protects even where it gets scratched.
3. The body of a car
  Show solution
  AnswerPainting (over a primer)
  Paint forms a barrier and gives a good finish; many car bodies are also galvanised underneath.
Quick answerEasyNCERT Exercises Q11
Carbon dioxide dissolves in water to give a solution with a pH below 7. This shows that oxides of non-metals are generally
basicacidic (a few are neutral)amphotericalkaline
Show answer
Answer (B) acidic (a few are neutral)
Non-metal oxides such as $C O_{2}$ and $S O_{2}$ are acidic. A few, such as carbon monoxide, are neutral.
12
Short answerMediumNCERT Exercises Q12
Give reasons.
1. Silver and gold coins from ancient times are still found in good condition.
  Show solution
  Silver and gold are near the bottom of the reactivity series, so air and water barely attack them. They keep their shape and lustre for centuries.
2. A teacher keeps potassium under paraffin oil, never in water.
  Show solution
  Potassium reacts violently with water and quickly with air, and the hydrogen formed can catch fire. Paraffin oil does not react with it and keeps both air and moisture away.
3. Aluminium is high in the reactivity series, yet pressure-cooker bodies are made of it.
  Show solution
  A thin, tough layer of aluminium oxide forms on the surface and stops further reaction. Aluminium is also light and a good conductor of heat.
4. Galena (PbS) is converted into lead(II) oxide before lead is extracted.
  Show solution
  It is much easier to reduce a metal oxide (with carbon) than a sulphide, so the sulphide ore is first roasted to the oxide.
Short answerMediumNCERT Exercises Q13
Brass diyas turn dull and greenish some weeks after Diwali. Why does rubbing them with a paste of lemon juice (or tamarind) and salt make them shine again?
Show solution
AnswerThe acid dissolves the basic copper carbonate (or oxide) coat.
The dull green or dark coating is basic copper carbonate (and copper oxide), formed by the reaction of copper in the brass with moist air. These compounds are basic.
Lemon juice contains citric acid and tamarind contains tartaric acid. The acid reacts with the basic coating, turning it into salts that wash away with water, and the fresh shiny metal beneath is exposed.
Long answerMediumNCERT Exercises Q14
Compare a metal and a non-metal on three chemical points: the oxide formed, the ion formed, and the reaction with dilute acids. Use sodium and sulphur as examples, and name one hydride formed by a non-metal.
Show solution
AnswerBasic vs acidic oxide; positive vs negative ion; displaces hydrogen vs does not.
Table 3.12
Point Sodium (metal) Sulphur (non-metal)
Oxide $N a_{2} O$ , basic; gives NaOH $S O_{2}$ , acidic; gives $H_{2} S O_{3}$
Ion loses 1 electron: $N a^{+}$ gains 2 electrons: $S^{2 -}$
Dilute acids displaces hydrogen (violently) no hydrogen
Non-metals combine with hydrogen to form hydrides, for example hydrogen sulphide, $H_{2} S$ .
15
Short answerHardNCERT Exercises Q15
A roadside polisher offers to make a dull pair of gold earrings shine 'like new'. He dips them for a minute in a fuming yellowish liquid, rinses them and hands them back gleaming. At home the earrings weigh 9.2 g instead of 10.0 g.
1. Which liquid did he probably use?
  Show solution
  AnswerAqua regia
  Aqua regia, made fresh from three parts of concentrated $H C l$ to one part of concentrated $H N O_{3}$ , is one of the very few liquids that dissolve gold.
2. What percentage of the mass of the earrings was lost?
  %
  Show solution
  Loss $= 10.0 - 9.2 = 0.8 g$ , so the percentage lost is $0.8 / 10.0 \times 100 = 8 %$ . That gold stayed behind in his liquid.
3. Why does neither of the two acids in the liquid do this on its own?
  Show solution
  AnswerOnly the mixture dissolves gold.
  Gold is so unreactive that neither concentrated acid alone attacks it; only the mixture, aqua regia, can dissolve it. The fresh gold surface underneath then shines.
Short answerMediumNCERT Exercises Q16
Solar water heaters and geysers often use copper tanks, or tanks lined with copper, rather than plain steel. Give two reasons.
Show solution
AnswerCopper does not react with hot water; it conducts heat well.
Copper is below hydrogen in the reactivity series and does not react with water, even hot water. Steel, which is mostly iron, would rust in hot water containing dissolved air.
Copper is also an excellent conductor of heat, so the water warms up quickly.
Quick answerMedium
Assertion (A): Aluminium vessels do not corrode easily, although aluminium is a reactive metal. Reason (R): A thin layer of aluminium oxide on the surface protects the metal beneath.
Both A and R are true, and R explains ABoth A and R are true, but R does not explain AA is true, but R is falseA is false, but R is true
Show answer
Answer (A) Both A and R are true, and R explains A
Both statements are true, and the protective oxide layer is exactly why aluminium resists corrosion.
Quick answerMedium
Assertion (A): Copper does not give hydrogen with dilute hydrochloric acid. Reason (R): Copper is above hydrogen in the reactivity series.
Both A and R are true, and R explains ABoth A and R are true, but R does not explain AA is true, but R is falseA is false, but R is true
Show answer
Answer (C) A is true, but R is false
A is true, but copper is below hydrogen, so R is false. Being below hydrogen is why copper gives no hydrogen.
Quick answerEasy
Heating a carbonate ore in little or no air is called , and heating a sulphide ore in plenty of air is called .
Show answer
Answer (1) calcination, (2) roasting
Calcination is for carbonates in limited air; roasting is for sulphides in excess air.
Quick answerMedium
An aluminium atom has atomic number 13. How many electrons does it lose when it forms an ion?
electrons
Show answer
Answer 3 electrons
Aluminium is 2, 8, 3. Losing the three outer electrons leaves 2, 8, a full octet, so it forms $A l^{3 +}$ .

Point	Sodium (metal)	Sulphur (non-metal)
Oxide	$N a_{2} O$ , basic; gives NaOH	$S O_{2}$ , acidic; gives $H_{2} S O_{3}$
Ion	loses 1 electron: $N a^{+}$	gains 2 electrons: $S^{2 -}$
Dilute acids	displaces hydrogen (violently)	no hydrogen

Find your NCERT exercise question

Our practice questions are written for ncert.ai and follow the NCERT exercises. Find the one that matches the question in your textbook; its answer is with it.

In your NCERT textbook	Practice question here
NCERT in-text Questions p. 40, Q1	Practice: physical properties (NCERT in-text questions, p. 40) · Q1
NCERT in-text Questions p. 40, Q2	Practice: physical properties (NCERT in-text questions, p. 40) · Q2
NCERT in-text Questions p. 46, Q1	Practice: reactivity (NCERT in-text questions, p. 46) · Q1
NCERT in-text Questions p. 46, Q2	Practice: reactivity (NCERT in-text questions, p. 46) · Q2
NCERT in-text Questions p. 46, Q3	Practice: reactivity (NCERT in-text questions, p. 46) · Q3
NCERT in-text Questions p. 46, Q4	Practice: reactivity (NCERT in-text questions, p. 46) · Q4
NCERT in-text Questions p. 46, Q5	Practice: reactivity (NCERT in-text questions, p. 46) · Q5
NCERT in-text Questions p. 49, Q1	Practice: ionic compounds (NCERT in-text questions, p. 49) · Q1
NCERT in-text Questions p. 49, Q2	Practice: ionic compounds (NCERT in-text questions, p. 49) · Q2
NCERT in-text Questions p. 53, Q1	Practice: occurrence and extraction (NCERT in-text questions, p. 53) · Q1
NCERT in-text Questions p. 53, Q2	Practice: occurrence and extraction (NCERT in-text questions, p. 53) · Q2
NCERT in-text Questions p. 53, Q3	Practice: occurrence and extraction (NCERT in-text questions, p. 53) · Q3
NCERT in-text Questions p. 55, Q1	Practice: corrosion and alloys (NCERT in-text questions, p. 55) · Q1
NCERT in-text Questions p. 55, Q2	Practice: corrosion and alloys (NCERT in-text questions, p. 55) · Q2
NCERT in-text Questions p. 55, Q3	Practice: corrosion and alloys (NCERT in-text questions, p. 55) · Q3
NCERT Exercises Q1	Exercises · Q1
NCERT Exercises Q2	Exercises · Q2
NCERT Exercises Q3	Exercises · Q3
NCERT Exercises Q4	Exercises · Q4
NCERT Exercises Q5	Exercises · Q5
NCERT Exercises Q6	Exercises · Q6
NCERT Exercises Q7	Exercises · Q7
NCERT Exercises Q8	Exercises · Q8
NCERT Exercises Q9	Exercises · Q9
NCERT Exercises Q10	Exercises · Q10
NCERT Exercises Q11	Exercises · Q11
NCERT Exercises Q12	Exercises · Q12
NCERT Exercises Q13	Exercises · Q13
NCERT Exercises Q14	Exercises · Q14
NCERT Exercises Q15	Exercises · Q15
NCERT Exercises Q16	Exercises · Q16

Quick check: MCQs on Metals and Non-metals

3.1.2 Non-metals4 questions
3.2.2 What happens when Metals react with Water?4 questions
3.2.5 The Reactivity Series4 questions
3.3.1 Properties of Ionic Compounds4 questions
3.4.6 Refining of Metals4 questions
3.5.1 Prevention of Corrosion4 questions

Glossary · 15

Key terms (English–Hindi)

alloyमिश्रातुmishraatu: A metal blended evenly with other metals or with a non-metal, such as brass or steel.First seen in the chapter →
amphoteric oxideउभयधर्मी ऑक्साइडubhaydharmi oxide: A metal oxide, such as $A l_{2} O_{3}$ or $Z n O$ , that reacts with both acids and bases to give a salt and water.First seen in the chapter →

calcinationनिस्तापनnistaapan: Heating a carbonate ore strongly in little or no air to turn it into the oxide.First seen in the chapter →
corrosionसंक्षारणsankshaaran: The slow eating away of a metal by air, moisture or chemicals around it; rusting of iron is an example.First seen in the chapter →

ductileतन्यtanya: Able to be stretched into fine wire; gold can be drawn finer than any other metal.First seen in the chapter →

electrolytic refiningविद्युत-अपघटनी परिष्करणvidyut-apghatani parishkaran: Purifying a metal by electrolysis, with impure metal as the anode and pure metal as the cathode.First seen in the chapter →

galvanisationयशदलेपनyashadlepan: Giving iron or steel a thin coat of zinc to stop it rusting.First seen in the chapter →
gangueगैंगgaing: The soil, sand and rock mixed with an ore, removed before the metal is extracted.First seen in the chapter →

ionic compoundआयनिक यौगिकaayanik yaugik: A compound of positive and negative ions held by electrostatic attraction, formed by electron transfer from a metal to a non-metal.First seen in the chapter →

malleableआघातवर्ध्यaaghaatvardhya: Able to be beaten or rolled into thin sheets without breaking, as gold, silver and aluminium are.First seen in the chapter →
metallurgyधातुकर्मdhaatukarm: Getting metals out of their ores and purifying them for use.First seen in the chapter →
mineralखनिजkhanij: A naturally formed element or compound found in the Earth's crust.First seen in the chapter →

oreअयस्कayask: A mineral from which a metal can be extracted profitably.First seen in the chapter →

reactivity seriesसक्रियता श्रेणीsakriyata shreni: A list of metals from the most reactive (potassium) to the least reactive (gold), with hydrogen placed in it for comparison.First seen in the chapter →
roastingभर्जनbharjan: Heating a sulphide ore strongly in plenty of air to turn it into the oxide.First seen in the chapter →

3.1 Physical Properties

3.1.1 Metals

3.1.2 Non-metals

3.2 Chemical Properties of Metals

3.2.1 What happens when Metals are burnt in Air?

3.2.2 What happens when Metals react with Water?

3.2.3 What happens when Metals react with Acids?

3.2.4 How do Metals react with Solutions of other Metal Salts?

3.2.5 The Reactivity Series

3.3 How do Metals and Non-metals React?

3.3.1 Properties of Ionic Compounds

3.4 Occurrence of Metals

3.4.1 Extraction of Metals

3.4.2 Enrichment of Ores

3.4.3 Extracting Metals Low in the Activity Series

3.4.4 Extracting Metals in the Middle of the Activity Series

3.4.5 Extracting Metals towards the Top of the Activity Series

3.4.6 Refining of Metals

3.5 Corrosion

3.5.1 Prevention of Corrosion

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Quick check: MCQs on Metals and Non-metals

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