ICSE Class 8 Chemistry Chapter 5 Metals and Non Metals

1. State: Metals are crystalline solids (except mercury, which is a liquid).

State: Non-metals are either gases or solids [Exception: Bromine is a liquid].

2. Metallic lustre: In their pure state, metals shine. This property is called metallic lustre. In other words, metals can be polished.

Lustre: Non-metals are dull to look at, i.e. they cannot be polished [Exceptions: Graphite and iodine are lustrous].

3. Density: Metals have high density (except sodium, potassium and lithium).

Density: Non-metals have low density [Exception: Diamond has high density].

4. Hardness: Metals are hard solids (except sodium and potassium, which are soft and can be cut with a knife). (But zinc is brittle, i.e. it breaks into pieces when it is hammered).

Hardness: Non-metals are not hard. If solid they are soft and brittle. For example, phosphorus and sulphur are soft solids and iodine is brittle [Exception: Diamond is the hardest natural substance].

5. Melting point: Metals have high melting points.

Melting point and boiling point: Non-metals have both low melting and low boiling points [Exceptions: Carbon, silicon and boron have both high melting and high boiling points].

6. Malleability: Metals are malleable, i.e. they can be hammered into sheets. Gold, silver, copper, aluminium and tin can be beaten into very thin sheets called foils. (But zinc is brittle, i.e. it breaks into pieces when it is hammered).

Malleability: Non-metals are non-malleable. When they are hammered they turn into a powder, i.e. non-metals are of a brittle nature.

7. Ductility: Metals are ductile, i.e. they can be drawn into wires. Gold, silver, copper and aluminium are highly ductile metals, gold being the most ductile of all metals. [Exception: Zinc, arsenic and antimony i.e., metalloids cannot be drawn into wires].

Ductility: Non-metals are not ductile [Exception: Carbon fibre, a recently developed allotrope of carbon, is ductile].

8. Tensile strength: Metals have high tensile strength, i.e. they can bear a lot of strain [Exception: Zinc].

Tensile strength: Non-metals have low tensile strength [Exception: Carbon fibre has high tensile strength].

9. Thermal and electrical conductivity: Metals are good conductors of heat and electricity. Silver is the best conductor of heat and electricity. Tungsten is a bad conductor of electricity while lead is a bad conductor of heat.

Thermal and electrical conductivity: Non-metals are bad conductors of heat and electricity [Exceptions: Graphite is a good conductor of heat and electricity. Gas carbon is a good conductor of electricity].

10. Sonority: Metals produce a twangy sound when they are struck with a hard object, i.e. they are sonorous substances.

Sonority: Solid non-metals do not produce a sound when they are struck, i.e. they are not sonorous substances.

11. Solubility: Metals are usually insoluble in water or in organic solvents.

Solubility: With regard to solubility in water or organic solvents there is no fixed rule that applies to the non-metals. For example, chlorine is soluble in water, but sulphur, carbon and phosphorus are not.

1. Electronic configuration: A metal has 1, 2 or 3 electrons in their valence shell.

1. Electronic configuration: Non-metallic atom have 4, 5, 6 or 7 electrons in there valence shells. [Exception: Hydrogen and helium have one and two electron in their valence shells respectively.]

2. Valency: Metals have valencies +1, +2 or +3. They lose valence electrons during chemical combination to form electropositive ions (cations).

Na - e- → Na+, Mg - 2e- → Mg2+

(valency + 1) (valency + 2)

Al - 3e- → Al3+

(valency + 3)

2. Valency: Non-metals have valencies -1, -2 or -3. They gain electrons in their valence shells during chemical combination to complete their octet and form electronegative ions (anions).

Cl + e- → Cl-, O + 2e- → O2-

(valency + 1) (valency + 2)

N + 3e- → N3-

(valency + 3)

Carbon is tetravalent

3. Reducing nature: Metals are good reducing agents since they lose their valence electrons.

3. Oxidising nature: Non-metals are good oxidising agents since they gain electrons. [Exception: H2 and carbon act as reducing agents]

4. Atomicity: Molecules of metals are usually monoatomic.

4. Atomicity: Molecules of non-metals are usually polyatomic. [Exception: Inert gases are monoatomic].

5. Reaction of metals with oxygen and nature of oxide: In presence of heat most metals react with oxygen (or air) to form their respective oxides. These metallic oxides are of basic nature. Therefore they are also known as basic oxides. Some of these oxides dissolve in water to produce alkali. These basic oxides react with acids to produce salt and water.

Metal + Oxygen - heat → Oxide (Basic)

2Cu + O2 → 2CuO

(Basic oxide)

CuO + H2SO4 → CuSO4 + H2O

(Salt) (Water)

(i) Metals like sodium and potassium react vigorously with oxygen (even in absence of heat) to form their oxides. Calcium too forms its oxide without being heated.

5. Reaction of non-metals with oxygen and nature of oxides: Non metals react with oxygen (or air) on heating to form their respective oxides. Most of these oxides are acidic in nature and they turn moist blue litmus paper into red. They react with bases to produce salt and water.

Non metal + Oxygen - heat → Non metallic oxide

(i) Carbon burns in oxygen to produce carbon dioxide.

C + O2 - heat → CO2

(Carbon) (Oxygen) (Carbon dioxide)