### Theory:

The elements in the periodic table are classified as metals and non-metals based on their physical and chemical properties. There are around $$95$$ metals and $$17$$ non-metals in the periodic table.
Non-metals are electronegative elements where they gain electrons to form a stable configuration.
Physical properties of Non-metals:
A physical property can be observed and measured without altering the sample's chemical identity. A physical property can cause a physical change but not a chemical change.

Let us see some of the physical properties of Non-metals:
• State
• Lustre
• Malleability
• Ductility
• Hardness
• Valency
• Conduction
• Density
• Sonorous
• Melting point and boiling point
State:

Most of the non-metals exist in all three states of matter at room temperature. For example, carbon (solid), bromine (liquid) and chlorine (gas).

Chlorine gas

Lustre:

Non-metals are non-lustrous (as they have no metallic lustre and do not reflect light) in nature, except iodine and diamond.

Diamond

Malleability:

Non-metals are non-malleable (as they are very brittle, they cannot be drawn into sheets)in nature, except carbon.

Carbon

Ductility:

Non-metals are non-ductile (as they are very brittle, they cannot be drawn into wires) in nature.

Brittle nature of non-metal

Hardness:

Non-metals are soft except diamond.

Sulphur

Valency:

Non-metals have $$4$$ to $$7$$ electrons in the outermost shell.

Electronic configuration of non-metal

Conduction:

Non-metals are poor conductors of heat and electricity except graphite.

Insulators

Density:

Non-metals have low density.

Graphite

Sonorous:

Non-metals make a dull sound.

Plastics

Melting and Boiling point:

Non-metals have low melting and boiling points except sodium and potassium, which have low melting and boiling points.

Low melting point of non-metal
The materials which generally possess the above properties are called Non-metals.
Example:
Oxygen, carbon, sulfur, hydrogen, phosphorous, nitrogen, chlorine etc.