Compounds are pure substances whereas mixtures are impure substances. The constituents of a compound are present in a fixed ratio but mixture are are made up of two or more substances mixed physically.
Covalent compounds are formed by the mutual sharing of electrons by the combining atoms. Formation of some typical covalent compound is described below:
Petro/diesel used in automobiles contains tetraethyl lead, (C2H5)4Pb. Tetraethyl lead acts as an anti-knocking agent. Anti-knocking agent such as, tetraethyl lead is added to petrol/diesel to make its combustion smoother.
Some important characteristics of ionic (or electrovalent) compounds are :- Ionic (or electrovalent) compounds have relatively high density. In ionic compounds, the ions are closely packed. This decreases the volume of the system, and as a result density is high.
When there is a transfer of electrons from one atom to another either by gain or loss of electrons an ionic or electrovalent bond is formed. An ionic bond is a bond between ions with opposite charges.
Mixtures differ from compounds as follows: A mixture is heterogeneous, except solutions which are homogeneous whereas a chemical compound is always homogeneous.