Dalton’s Atomic Theory

Limitations of Dalton’s Theory 

 • It fails to explain why atoms of different kinds should differ in mass and valency etc.

 • The discovery of isotopes and isobars showed that atoms of same elements may have different atomic masses (isotopes) and atoms of different kinds may have same atomic masses (isobars).

 • The discovery of various sub-aomic particles like X-rays, electrons, protons etc. during late 19th century lead to the idea that the atom was no longer an indivisible and smallest particle of the matter.