Physical Properties of Non-metals

Physical Properties of Non-metals

Below are the properties of non metals:

Physical state: Most of the non-metals exist in two of the three states of matter at room temperature: gases (oxygen) and solids (carbon). These have no metallic lustre, and do not reflect light.

Nature: Non-metals are very brittle, and cannot be rolled into wires or pounded into sheets.

Conduction: They are poor conductors of heat and electricity.

Electronegative Character: Non-metals have a tendency to gain or share electrons with other atoms. They are electronegative in character.

Reactivity: They generally form acidic or neutral oxides with oxygen.

Metals and Non-Metals - Compared

A detailed comparison of properties of metals and non-metals is given in table:

Property	Metals	Non-metals
State of matter	These are usually solid, except mercury, which is a liquid at room temperature. Gallium and Caesium melt below 30. So if room temperature is around 30, they may also be in liquid state	These exist in all the three states. Bromine is the only liquid.
Density	They usually have high density, except for sodium, potassium, calcium etc.	Their densities are usually low.
Melting point	They usually have a high melting point except mercury, cesium, gallium, tin, lead.	Their melting points are low.
Boiling point	Their boiling points are usually high.	Their boiling points are low.
Hardness	They are usually hard, except mercury, sodium, calcium, potassium, lead etc.	They are usually not hard. But the exception is the non-metal diamond, the hardest substance.
Malleability	They can be beaten into thin sheets.	They are generally brittle.
Ductility	They can be drawn into thin wires, except sodium, potassium, calcium etc.	They cannot be drawn into thin wires.
Conduction of heat	They are good conductors of heat.	They are poor conductors of heat.
Conduction of electricity	They are good conductors of electricity.	They are non-conductors, except for carbon in the form of graphite and the gas carbon.
Lustre	Newly cut metals have high lustre. Some get tarnished immediately.	Usually not lustrous, except iodine and diamond - the most lustrous of all the substances.
Alloy formation	They form alloys.	Generally, they do not form alloys. However carbon, phosphorus, sulphur etc. can be present in some alloys.
Tenacity	These usually have high tensile strength except sodium, potassium, calcium, lead etc.	These have low tensile strength.
Brittleness	They are hard but not brittle, except zinc at room temperature.	They are generally brittle.
Electronic configuration	They usually have 1, 2 or 3 electrons in their valence shell. The greater the number of shells and lesser the number of valence electrons, the greater is the reactivity of the metal.	They usually have 4, 5, 6 or 7 electrons in the valence shell. If it has 8 electrons, it is called a noble gas. Lesser the number of shells and greater the number of valence electrons, greater is the reactivity of the non-metal.
Ionization	They always ionize by losing electrons:	They always ionize by gaining electrons:
Charge of ions	Positively charged.	Negatively charged.
Type of valency	Metals always exhibit electrovalency.	Non-metal exhibit both electrovalency or covalency.
Deposition during electrolysis	They are always deposited at the cathode.	They are always deposited at the anode.
Redox reaction	These lose electrons and hence get oxidized.	These gain electrons and hence get reduced.
Redox agents	They are reducing agents.	They are oxidizing agents.
Nature of oxides	They generally form basic oxides, some of which are also amphoteric, such as aluminium oxide, zinc oxide, lead oxide etc.	They generally form acidic oxides. Some oxides are neutral, such as nitrous oxide, nitric oxide, carbon monoxide water etc.
Hydrides	They usually do not form hydrides except those of sodium, potassium and calcium.	They do form hydrides, e.g. NH3, PH3, HCl, HBr, HI, H2S, H2O etc.
Atomicity	These are always monatomic.	These can be mono, di, tri, or polyatomic.
Solubility	They do not dissolve in solvents except by chemical action.	They dissolve in solvents and can be re-obtained by evaporation. Example: Sulphur in carbon disulphide.
Action with chlorine	They produce chlorides, which are electrovalent.	They produce chlorides, which are covalent.
Action with dilute acids	On reaction with dilute acids they give respective salt and hydrogen.	They do not react with dilute acids.