What are covalent compounds? Why are they different from ionic compounds? List their three characteristic properties.

Compounds containing covalent bonds (i.e. bonds formed by haring of electrons between two atoms) are known as covalent compounds. Covalent compounds are formed by sharing electrons between atoms. These are formed by molecules and hence also called molecular compounds. Example- methane, ethane, water etc.

There are various differences between covalent and ionic compounds as mentioned below-

The three characteristic properties of covalent compounds are as follows-

a) Covalent compounds are usually liquids or gases- due to weak forces of attraction between their molecules. Only some of them are solids for example alcohol, ether, benzene, bromine are liquids, methane, ethane, ethyne are gases. Glucose, sugar, iodine are solid covalent compounds.

b) They have low melting points and boiling points- since these are made up of electrically neutral molecules, so the forces of attraction between the molecules of covalent compounds are very weak. Only a small amount of heat can break it due to which they have low melting and boiling points for example- carbon tetrachloride has low melting point of 77° C.

c) These do not conduct electricity- which means these are non-electrolytes. Conduction does not occur since the compounds do not contain ions. For example- sugar, urea etc. do not conduct.

Examples:

Ionic Compounds: NaCl, MgCl₂

Covalent Compounds: O₂, H₂O