Physical Properties of Non-metal

1. Physical State: Nonmetals can exist as solids, liquids, or gases at ordinary temperatures.

Examples,

• Solids: Carbon (C), Sulfur (S), Phosphorus (P)
• Liquids: Bromine (Br₂)
• Gases: Hydrogen (H₂), Nitrogen (N₂), Oxygen (O₂)

2. Lustre: Nonmetals generally do not have a shiny appearance.

Exceptions: Diamond and iodine crystals have a lustrous, shiny look.

Colours: Nonmetals vary in colour.

• Carbon (as coal) is black.
• Sulphur is yellow.
• Bromine is brown.
• Some nonmetals, like oxygen and nitrogen, are colourless.

3. Brittleness: Solid nonmetals are brittle, meaning they break easily when hammered. Some nonmetals are soft, but diamond (an allotrope of carbon) is an exception. It is the hardest natural substance.

Example, 

If you hammer coal (a form of carbon), it breaks into pieces.

4. Ductility & Malleability: Nonmetals cannot be drawn into thin wires (not ductile). They also cannot be beaten into sheets (not malleable).

5. Conduction of Heat & Electricity: Nonmetals are poor conductors of heat and electricity. Exception: Graphite (another form of carbon) is an excellent conductor of electricity.

6. Density: Nonmetals usually have low density, making them light substances.

7. Melting & Boiling Point: Most nonmetals have low melting and boiling points, which means they melt and boil at lower temperatures. Exceptions: Some solid nonmetals, like carbon and boron, have very high melting points.

• Most metals are solids at room temperature, but mercury is a liquid, and gallium and caesium melt in the palm of the hand due to their very low melting points.
• Alkali metals (lithium, sodium, potassium) are soft, low-density metals with low melting points, unlike most metals.
• Iodine, though a non-metal, shows a metallic lustre, which is unusual for a non-metal.
• Carbon exists in allotropes: diamond is the hardest natural substance, and graphite is a good conductor of electricity.
• Nonmetals are usually non-lustrous, soft, poor conductors, and exist in solid or gas states, with bromine being the only liquid non-metal.