According to Dalton’s atomic theory, all matter, whether an element, a compound or a mixture is composed of small particles called atoms.
The postulates of this theory may be stated as follows:
(i) All matter is made of very tiny particles called atoms, which participate in chemical reactions.
(ii) Atoms are indivisible particles, which cannot be created or destroyed in a chemical reaction.
(iii) Atoms of a given element are identical in mass and chemical properties.
(iv) Atoms of different elements have different masses and chemical properties.
(v) Atoms combine in the ratio of small whole numbers to form compounds.
(vi) The relative number and kinds of atoms are constant in a given compound.