John Dalton in the year 1808 proposed the atomic theory which state that:
1.All matter is made up of indivisible particular called atom
2.Atom can neither be created nor destroyed in a chemical reaction
3.Atom of the same element are alike in every aspect and differ from atom of all other elements
4.When atom combine to form compound they do so in simple ratio
5.A chemical reaction is as a result of rearrangement,combination and separation of atoms.
These experimental evidence was supported by the law of chemical combination.
It's limitation was that it could not account for electrolysis and other phenomenon.As a result of new discoveries this theory has undergo several modifications which are:
1.Due to the discovery of sub-atomic particles,the theory of atom been indivisible no more hold.
2.Atom can neither be created nor destroyed only hold for ordinary chemical reaction.however this statement does not hold for nuclear reactions
3.Atom of the same element are alike in every aspect and differ from those of different elements is unacceptable due to the discovery of isotopes
4.During a chemical reaction there is a combination of atom in small whole number.This statement stand true for inorganic compound however organic compounds do not obey this theory.
5.A chemical reaction is as a result of rearrangement,combination and separation,is the only theory that still stand true.
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