DALTON'S & MODERN ATOMIC THEORY

DALTON'S ATOMIC THEORY                                     


       In the year 1808 John Dalton proposed a theory on the nature of matter.

It stated that,all matters are made up of small individual particles known as atom.

(I) Postulates of Dalton's atomic theory

Matter is made up of very small individual particles called atom.

Atoms of the same elements are indentical in all respect.

Atoms can neither be created nor destroyed,also it cannot be divided into small particles.

Atoms can be rearranged,combined or separated in chemical reaction.

(ii) Limitations of Dalton's atomic theory

 It doesn't explain the cause of chemical combination.

It fails to explain gaseous volume.

It doesn't give the ideas of isotopes and isobars.

It doesn't give any ideas about the structure of atom.

This theory doesn't account for allotropes.

MODERN ATOMIC THEORY

(1) Atoms are composed still smaller particles which are called electrons, protons and neutrons.

(2) Atoms of the same elements may not be similar on all respect.

(3) Atoms of the different elements may have the same atomic masses.

(4) Atoms of the different elements may not combine in simple ratio.

(5) Mass and energy are inter convertable.

(6) Atoms of the one element can be changed into atoms of the other elements.


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