Mention the postulates and limitations of Dalton's atomic theory.

Explanation

The main postulates of Dalton 's atomic theory are :
(i) Matter is composed of tiny indivisible particles called atoms . They cannot be created or destroyed or transformed into atoms of another element.
(ii) Atoms of a given element are identical in all respects.
(iii) Atoms of different elements are different from each other in all respects.
(iv) Atoms of different elements take part in the chemical reaction and combine in a simple integral ratio to form compounds.
(v) When elements react , the atoms may combine in more than one simple whole number ratio.
Dalton 's atomic theory has been contradicted with the advancement of science and modified on the basis of further research and discoveries.
Limitations of Dalton 's atomic theory
(i) With the discovery of subatomic particles , that is the electron , proton and neutron , it was concluded that atoms can be further divided.
(ii) Discovery of isotopes proved that atoms of the same element may possess different atomic weights, that atoms of same elements may not be identical in all respects . for example isotopes of hydrogen namely , protium `(._(1)H^(1))` deuterium `(._(1)H^(2))`
(iii) In some cases , atoms of different elements are found to have same mass number that is atoms of different elements may be identical . For example , calcium and argon are found to have same mass number.