METALS AND NON METALS

Metals and Non-Metals

Introduction

Elements are broadly classified into:

• Metals

• Non-Metals

• Metalloids (have properties of both metals and non-metals)

Physical Properties of Metals

Property	Description	Examples
1. Lustre (Shiny appearance)	Metals have a shiny surface. They can be polished.	Gold, Silver, Copper
2. Hardness	Most metals are hard (except sodium & potassium – soft metals).	Iron is hard; Na, K are soft.
3. Malleability	Metals can be beaten into thin sheets.	Aluminium foil, gold foil
4. Ductility	Metals can be drawn into wires.	Copper wire, aluminium wire
5. Conductivity	Metals are good conductors of heat & electricity.	Silver, copper
6. Sonorous	Produce ringing sound when struck.	Bells are made of metals
7. High Density and Melting Point	Most metals are dense and have high melting points.	Tungsten has the highest melting point.

Exceptions:

• Mercury (liquid metal)

• Sodium and Potassium (soft)

• Lead and Mercury (poor conductors)

Physical Properties of Non-Metals

Property	Description	Examples
1. Lustre	Non-metals are dull (except iodine).	Sulphur, Carbon
2. Hardness	Generally soft (except diamond – hardest natural substance).	Graphite is soft
3. Malleability & Ductility	Non-metals are brittle, not malleable or ductile.	Sulphur breaks easily
4. Conductivity	Poor conductors of heat and electricity (except graphite).	Graphite conducts electricity
5. Melting & Boiling Points	Generally low melting and boiling points.	Sulphur melts easily
6. Density	Usually have low density.	Oxygen, nitrogen are gases

Chemical Properties of Metals

1. Reaction with Oxygen

Metals form metal oxides when burnt in air.

Example:
[
4Na + O_2 → 2Na_2O
]
[
2Mg + O_2 → 2MgO
]

Metal oxides are generally basic and form alkalies with water.
[
Na_2O + H_2O → 2NaOH
]

Amphoteric oxides react with both acids and bases:
Examples: Al₂O₃, ZnO

2. Reaction with Water

Some metals react with water to form metal hydroxides and hydrogen gas.

Metal	Reaction	Example
Very reactive	Reacts with cold water	Na, K
Moderately reactive	Reacts with steam	Fe, Zn
Less reactive	No reaction with water	Cu, Ag, Au

Example:
[
2Na + 2H_2O → 2NaOH + H_2↑
]

3. Reaction with Acids

Metals react with dilute acids to produce hydrogen gas.

[
Zn + 2HCl → ZnCl_2 + H_2↑
]

Hydrogen test: Bring a burning matchstick → produces a pop sound.

Note: Cu, Ag, Au do not react with dilute acids.

4. Reaction with Other Metal Salts (Displacement Reaction)

A more reactive metal displaces a less reactive metal from its compound.

[
Fe + CuSO_4 → FeSO_4 + Cu
]

This is used to arrange metals in a Reactivity Series.

Reactivity Series (Most Reactive → Least Reactive)

Order	Metal
1	Potassium (K)
2	Sodium (Na)
3	Calcium (Ca)
4	Magnesium (Mg)
5	Aluminium (Al)
6	Zinc (Zn)
7	Iron (Fe)
8	Tin (Sn)
9	Lead (Pb)
10	(Hydrogen)
11	Copper (Cu)
12	Mercury (Hg)
13	Silver (Ag)
14	Gold (Au)
15	Platinum (Pt)

Occurrence of Metals

• Native State → Found pure in nature (e.g. Gold, Platinum)

• Combined State → Found as compounds (oxides, sulphides, carbonates)

Important Ores:

Metal	Ore	Formula
Aluminium	Bauxite	Al₂O₃·2H₂O
Iron	Haematite	Fe₂O₃
Zinc	Zinc Blende	ZnS
Copper	Copper Pyrite	CuFeS₂

Extraction of Metals

Steps:

1. Concentration of ore – removing impurities
   (e.g. washing, froth flotation)

2. Reduction – converting ore into metal

3. Refining – purifying the metal

Based on Reactivity:

Type of Metal	Extraction Method	Example
Highly reactive	Electrolysis	Na, K, Ca
Moderately reactive	Reduction with C/CO	Zn, Fe
Less reactive	Heating directly	Cu, Ag, Au

Corrosion

Slow destruction of metal by chemical reaction with air, moisture, etc.

Example:
Iron → Rusting
[
Fe + O_2 + H_2O → Fe_2O_3·xH_2O
]

Prevention:

• Painting

• Galvanisation (zinc coating)

• Alloying (mixing with other metals)

Alloys

Mixtures of two or more metals or metal + non-metal.

Alloy	Components	Use
Brass	Cu + Zn	Electrical fittings
Bronze	Cu + Sn	Statues, coins
Stainless Steel	Fe + C + Cr + Ni	Utensils, machines
Solder	Pb + Sn	Joining electrical wires

Uses of Metals and Non-Metals

Metals:

• Electrical wires (Cu, Al)

• Construction (Fe, Al)

• Jewellery (Au, Ag)

Non-Metals:

• Oxygen (respiration)

• Nitrogen (fertilisers)

• Chlorine (water purification)

• Sulphur (gunpowder, medicines)

Important Questions.

1. What are metals? Mention any three physical properties of metals.

1. Answer:
   Metals are elements that are electropositive, meaning they lose electrons to form positive ions.
   Properties:

   1. Metals are lustrous (shiny).

   2. They are good conductors of heat and electricity.

   3. They are malleable and ductile.

   2. What are non-metals? Mention any three physical properties of non-metals.

   Answer:
   Non-metals are elements that are electronegative and tend to gain electrons to form negative ions.
   Properties:

   1. Non-metals are non-lustrous (except iodine).

   2. They are poor conductors of heat and electricity (except graphite).

   3. They are non-malleable and non-ductile; they are brittle.

   3. Why are metals good conductors of electricity?

   Answer:
   Metals have free electrons which move easily inside the metal and carry electric current.
   Hence, metals are good conductors.

   4. Why is sodium stored in kerosene?

   Answer:
   Sodium reacts vigorously with air and moisture and may catch fire.
   To prevent this reaction, sodium is stored under kerosene.

   5. What happens when magnesium ribbon is burnt in air? Write the equation.

   Answer:
   Magnesium burns with a bright white flame and forms magnesium oxide, a white powder.

   Equation:
   
   2Mg + O2 → 2MgO
   
   

   6. Explain the reaction of metal with water with an example.

   Answer:
   Metals react with water to form metal hydroxide and hydrogen gas.
   Example: Sodium reacts vigorously.

   
   2Na + 2H2O → 2NaOH + H2↑
   
   

   7. What happens when iron reacts with copper sulphate solution?

   Answer:
   Iron is more reactive than copper. It displaces copper from copper sulphate solution and forms iron sulphate.

   Equation:
   
   Fe + CuSO4  → FeSO4 + Cu
   
   

   Solution turns green.

   8. What is corrosion? Give an example.

   Answer:
   Corrosion is the gradual eating up of metals due to reaction with air, moisture, or chemicals.
   Example: Rusting of iron.

   9. What is rusting? Write the conditions required for rusting.

   Answer:
   Rusting is the formation of hydrated ferric oxide on the surface of iron.

   Conditions:

   1. Moisture (water vapor)

   2. Oxygen

   10. What are alloys? Give two examples.

   Answer:
   An alloy is a homogeneous mixture of two or more metals or a metal with a non-metal.

   Examples:

   • Brass = Copper + Zinc

   • Steel = Iron + Carbon

   11. Why is aluminium more reactive than iron but does not corrode easily?

   Answer:
   Aluminium forms a thin protective layer of aluminium oxide (Al₂O₃) which prevents further corrosion.
   Iron does not form such a protective layer.

   12. Explain the ionic reaction between sodium and chlorine.

   Answer:
   Sodium loses 1 electron to form Na⁺.
   Chlorine gains 1 electron to form Cl⁻.
   They combine to form NaCl, an ionic compound.

   13. Why do ionic compounds have high melting and boiling points?

   Answer:
   Ionic compounds are held by strong electrostatic forces of attraction between positive and negative ions.
   A large amount of heat is required to break these bonds.

   14. Why do metals form basic oxides while non-metals form acidic oxides?

   Answer:
   Metals lose electrons and form basic oxides like MgO, Na₂O.
   Non-metals gain electrons and form acidic oxides like CO₂, SO₂.

   15. What happens when a non-metal reacts with oxygen? Give example.

   Answer:
   Non-metals form non-metallic oxides, which are acidic in nature