DALTON ‘S ATOMIC THEORY
 
  Main postulates of Dalton atomic theory is as follow:
  1. Matter is composed of very tiny or microscopic particles called "Atom".
  2. Atom is an indivisible particle.
  3. Atom can neither be created nor it is destroyed.
  4. Atoms of an element are identical in size, shape, mass and in other properties.
  5. Atoms of different elements are different in their properties.
  6. Atoms combine with each other in small whole numbers.
  7. All chemical reactions are due to combination or separation of atoms.

  DEFECTS IN DALTON’S THEORY:
  Postulate number 2, 3, 4 and 6 are not correct as described below:

  DEFECT NO: 1

  Atom can be divided into a number of sub-atomic particles such as electron, proton and neutron etc.

  DEFECT NO: 2

  Atoms of an element may be different in their masses.

  for example:

1H1, 1H2, 1H3

17Cl35, 17Cl37

  DEFECT NO: 3

  All compounds do not have small number of atoms.

  for example:

  • Decane C10H22.
  • Sugar C12H22O11.

  DEFECT NO: 4

  Atom can be destroyed by fission process in

Atom bomb.

Nuclear reactor.

  On the basis of above defects, Dalton's atomic theory has failed now.
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