Elements are classified broadly into two categories on the basis of properties:
Metals: Iron, Zinc, Copper, Aluminium etc.
Non – metals: Chlorine, Nitrogen, Hydrogen, Oxygen, Sulphur etc.
Apart from metals and non-metals, some elements show properties of both metals and non –metals,
e.g. Silicon, Arsenic, Germanium.They are called metalloids.
Comparison of physical properties of metals and non – metals:-
| Property | Metals | Non-Metals |
|---|---|---|
| Physical State | Metals are solid at room temperature. Except mercury and gallium. | Non-metals generally exist as solids and gases, except Bromine. |
| Melting and boiling points | Metals generally have high m.pt and b.pt except gallium and cesium. | Non-metals have low m.pt and b.pt except diamond and graphite. |
| Density | Generally high. | Generally low. |
| Malleability and Ductility | Malleable and ductile. | Neither malleable nor ductile. |
| Electrical and thermal conductivity | Good conductors of heat and electricity. | Generally poor conductors of heat and electricity except graphite. |
| Luster | Poses shining luster. | Do not have luster except iodine. |
| Sonorous sound | Give sonorous sound when struck. | Does not give sonorous sound. |
| Hardness | Generally hard except Na, K | Solid non-metals are generally soft except diamond. |