Reaction with Hydrogen
Non-metals react with hydrogen to form covalent hydrides. For example, nitrogen, oxygen, sulphur and chlorine react with hydrogen to form ammonia, water, hydrogen sulphide and hydrogen chloride, respectively.
The number of non-metals is much smaller, but they are the major constituents of air, ocean and earth. Oxygen is the most abundant element in the earth's crust, followed by silicon. The two non-metals constitute about 74.3% (by mass) of the earth's crust.
Reaction with Oxygen
Non-metals react with oxygen to form covalent oxides. For example, carbon forms carbon dioxide and sulphur forms sulphur dioxide.
Phosphorous burns with a bright dazzling flame giving white fumes of phosphorous pentoxide.
Carbon burns in oxygen giving carbon dioxide.
C + O2 CO2
The carbon dioxide gas, formed in this reaction turns lime water milky (white precipitate).
These oxides are acidic in nature, i.e. they react with water to form acids.
However some oxides of these non-metals, like carbon monoxide (CO) and nitrous oxide (N2O) are neutral.
Reaction with Acids
Reaction with ChlorineNon-metals react with chlorine to form covalent chlorides. For example, hydrogen reacts with chlorine to form hydrogen chloride and phosphorus reacts to form phosphorus trichloride.