1. Physical properties of metals

Metals generally have the following physical properties:

1. Lustrous: Metals are generally shiny in their pure state. This property is called lustre.

2. Malleable: Metals can be beaten into thin sheets. Gold and silver are among the most malleable metals.

3. Ductile: Metals can be drawn into thin wires. For example, 1 gram of gold can be drawn into a wire approximately 2 kilometres long under suitable conditions.

4. Conductors of heat: Most metals conduct heat well. Silver and copper are excellent conductors of heat, whereas lead and mercury are relatively poor conductors compared with many other metals.

5. High melting points: Most metals have high melting points. However, gallium and caesium have relatively low melting points and can melt near room temperature.

6. Conductors of electricity: Metals generally conduct electricity well. Copper and aluminium are commonly used in electrical wires.

7. Sonorous: Metals produce a ringing sound when struck against a hard surface.

Exceptions to the properties of metals

• Mercury is a metal that exists as a liquid at room temperature. Almost all other metals are solids at room temperature.

• Lithium, sodium and potassium are soft alkali metals that can be cut with a knife. They have low densities and relatively low melting points. They must be handled carefully because they react vigorously with water and air.

2. Physical properties of non-metals

Non-metals generally differ from metals in their physical properties. They are usually dull, brittle when solid, and poor conductors of heat and electricity. However, there are important exceptions.

1. Physical state: Non-metals may exist as solids or gases at room temperature. Bromine is the only non-metal that is liquid at room temperature.

2. Lustre: Most non-metals are dull, but iodine is a lustrous non-metal.

3. Allotropes of carbon: Carbon can exist in different forms called allotropes. Diamond and graphite are two important allotropes of carbon.

• Diamond: It is the hardest naturally occurring substance known and has very high melting and boiling points.

• Graphite: It conducts electricity, unlike most non-metals.

Common non-metals

Examples of non-metals include hydrogen, carbon, nitrogen, oxygen, phosphorus, sulphur and selenium.

Halogens

Halogens are a family of reactive non-metals belonging to Group 17 of the periodic table. They include:

• Fluorine

• Chlorine

• Bromine

• Iodine

• Astatine