Metals and Non-metals

Complete Chapter Notes in Simple Language

Chapter Overview: This chapter explains how metals and non-metals are classified by their physical and chemical properties, how metals react with air, water, acids and salt solutions, the reactivity series, ionic bonding, occurrence and extraction of metals, refining, corrosion and its prevention, and alloys.

📚 Chapter Contents

• Physical Properties of Metals
• Physical Properties of Non-metals
• Reaction of Metals with Air
• Reaction of Metals with Water
• Reaction of Metals with Acids
• Reaction with Salt Solutions
• The Reactivity Series
• How Metals and Non-metals React
• Properties of Ionic Compounds
• Occurrence of Metals
• Extraction of Metals
• Refining of Metals
• Corrosion
• Prevention of Corrosion & Alloys
• 20 Important Questions

Lustre, Malleability, Ductility

Metals, in their pure state, have a shining surface. This property is called metallic lustre. Metals that can be beaten into thin sheets show malleability, and metals that can be drawn into thin wires show ductility.

Hardness, Conductivity and Sonority

• Metals are generally hard, though hardness varies from metal to metal.
• Metals are good conductors of heat and electricity. Silver and copper are the best conductors of heat; lead and mercury are comparatively poor conductors.
• Metals that produce a ringing sound on striking a hard surface are said to be sonorous — this is why school bells are made of metal.

Important Exceptions

• Mercury is the only metal that is liquid at room temperature.
• Gallium and caesium have such low melting points that they can melt on the palm of your hand.
• Iodine is a non-metal but is lustrous.
• Alkali metals (lithium, sodium, potassium) are so soft they can be cut with a knife, and have low densities and low melting points.
• Carbon exists in different forms called allotropes — diamond is the hardest natural substance, while graphite conducts electricity.

There are very few non-metals compared to metals. Examples include carbon, sulphur, iodine, oxygen and hydrogen. Non-metals are either solids or gases, except bromine, which is a liquid.

Property	Metals	Non-metals
Malleability / Ductility	Yes	No, generally brittle
Conductivity	Good conductors	Poor conductors (except graphite)
Sonority	Sonorous	Not sonorous

Amphoteric Oxides

Metal oxides are generally basic. But some oxides, such as aluminium oxide and zinc oxide, react with both acids and bases — these are called amphoteric oxides.

Reactivity Towards Oxygen

• Potassium and sodium react so vigorously that they can catch fire in the open — hence stored under kerosene oil.
• Magnesium, aluminium, zinc and lead form a protective thin oxide layer that prevents further oxidation.
• Iron does not burn on heating, but iron filings burn vigorously when sprinkled in a flame.
• Copper does not burn but forms a black coat of copper(II) oxide.
• Silver and gold do not react with oxygen even at high temperatures.

Metal	Reaction with Water
Sodium, Potassium	React violently & exothermically with cold water; evolved H2 catches fire
Calcium	Reacts with cold water, less violently; floats due to H2 bubbles
Magnesium	No reaction with cold water; reacts with hot water
Aluminium, Iron, Zinc	React only with steam, giving metal oxide + H2
Lead, Copper, Silver, Gold	Do not react with water at all

The reactivity order observed with dilute acids (fastest to slowest) is:

Copper does not react with dilute HCl at all — no bubbles form and there is no temperature change.

Reactive metals can displace less reactive metals from their compounds in solution.

Example: an iron nail placed in copper sulphate solution shows the blue colour fading as copper is displaced and deposited on the nail — proving iron is more reactive than copper. A copper wire in iron sulphate solution shows no reaction.

The reactivity series lists common metals in order of decreasing chemical activity.

• Metals above hydrogen can displace hydrogen from dilute acids.
• Metals below hydrogen (copper, silver, gold) cannot displace hydrogen from dilute acids.
• A more reactive metal displaces a less reactive one from its salt solution.

Elements react to attain a completely filled valence shell (noble gas configuration). Metals achieve this by losing electrons to form cations; non-metals achieve this by gaining electrons to form anions.

Formation of Sodium Chloride

Sodium and chloride ions, being oppositely charged, attract each other by strong electrostatic forces to form NaCl. Sodium chloride does not exist as individual molecules but as aggregates of oppositely charged ions.

Formation of Magnesium Chloride

Property	Ionic Compounds
Physical nature	Solid, hard, and brittle (breaks under pressure)
Melting/Boiling points	High — strong inter-ionic attraction needs a lot of energy to break
Solubility	Soluble in water; insoluble in kerosene, petrol, etc.
Conduction (solid)	Do NOT conduct — ions cannot move in the rigid structure
Conduction (molten/solution)	DO conduct — ions become free to move

The earth's crust is the major source of metals; seawater also contains soluble salts like sodium chloride and magnesium chloride.

• Mineral — an element/compound occurring naturally in the earth's crust.
• Ore — a mineral from which a metal can be profitably extracted.
• Gangue — impurities (soil, sand) mixed with the ore.

Reactivity	Occurrence
Top of series (K, Na, Ca, Mg, Al)	Never found free — too reactive
Middle of series (Zn, Fe, Pb)	Found as oxides, sulphides or carbonates
Bottom of series (Cu, Ag, Au)	Often found free/native

Metals Low in Reactivity

Their oxides can be reduced by heating alone.

Metals in the Middle of the Series

Their sulphide/carbonate ores must first be converted to oxides:

• Roasting — heating a sulphide ore strongly in excess air.
• Calcination — heating a carbonate ore strongly in limited air.

Metals High in Reactivity

Obtained by electrolytic reduction of their molten compounds, since carbon cannot reduce their oxides.

The most widely used method for refining impure metals is electrolytic refining.

• Anode — impure metal
• Cathode — thin strip of pure metal
• Electrolyte — solution of the metal salt (e.g. acidified copper sulphate for copper)

• Silver reacts with sulphur in air, forming a black coating of silver sulphide.
• Copper reacts with moist CO₂, forming a green coat of basic copper carbonate.
• Iron forms a brown, flaky coating called rust when exposed to moist air.

Preventing Rust

Painting, oiling, greasing, galvanising (coating with zinc), chrome plating, anodising, or making alloys.

Alloys

An alloy is a homogeneous mixture of two or more metals, or a metal and a non-metal.

Alloy	Composition	Use
Stainless steel	Iron + Nickel + Chromium	Hard, rust-resistant
Brass	Copper + Zinc	Fittings, decorative items
Bronze	Copper + Tin	Statues, utensils
Solder	Lead + Tin	Welding electrical wires (low melting point)

1. What is metallic lustre? Give two examples of malleable metals.
2. Explain the meanings of malleable and ductile with examples.
3. Give an example of a metal that (i) is a liquid at room temperature (ii) can be cut with a knife.
4. What are amphoteric oxides? Give two examples.
5. Write balanced equations for the reaction of iron with steam and calcium with water.
6. Why is sodium kept immersed in kerosene oil?
7. Why does hydrogen gas not evolve when a metal reacts with nitric acid?
8. Name two metals which will displace hydrogen from dilute acids, and two which will not.
9. What is a displacement reaction? Give one example.
10. What is the reactivity series? Why is hydrogen included in it?
11. Explain, with an example, how an ionic compound like sodium chloride is formed.
12. Why do ionic compounds have high melting points?
13. Define the terms: (i) Mineral (ii) Ore (iii) Gangue.
14. What is roasting? What is calcination? Give one equation for each.
15. What is the thermit reaction? Where is it used?
16. In electrolytic refining of a metal M, what would you take as the anode, cathode and electrolyte?
17. State two ways to prevent the rusting of iron.
18. What are alloys? Give two examples with their composition and uses.
19. Why is copper used to make hot water tanks and not steel?
20. Give reasons: (i) Platinum, gold and silver are used to make jewellery. (ii) Aluminium is highly reactive yet used for cooking utensils.

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Metals and Non-metals

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