Dalton’s Atomic Theory

In the year 1808, John Dalton postulated the famous Atomic Theory and named after him ‘Dalton’s atomic theory’. Atoms are the indivisible building blocks of matter which cannot be destroyed. The atoms of the same element are identical. The atoms of different elements are not identical as they vary in mass and size.

Assumptions of Dalton’s atomic theory:

  • Each element consists of an extremely small particle. This small particle is called an atom. Each element is made up of an atom.
  • These extremely small particles present in the element are indivisible and cannot be created nor destroyed.
  • The atoms from the same element resemble each other whereas the atoms from different elements differ from each other.
  • The new chemical compounds are formed as a result of the rearrangement of already existing reactants.
  • The overall weight of the elements represents the overall weight of atoms.

Merits of Dalton’s atomic theory:

  • Laws of chemical combination can be well explained with Dalton’s theory.
  • Dalton was the first to distinguish between atom and molecule.

Drawbacks of Dalton’s theory:

  • According to Dalton’s theory, he said the atom is indivisible. But the atom can be divided into proton, electron, and neutron.
  • According to Dalton’s theory, he said that atoms of the same element have the same weight. But now the discovery has proved that atoms of the same element have different weights.
  • According to Dalton’s theory, he said the atoms of different elements have different masses. But now the discovery has proved that atoms of different elements can have the same weights.

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