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Question
Give the salient features of “Modern atomic theory”.
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Solution
(i) An atom is no longer indivisible.
(ii) Atoms of the same element may have different atomic mass.
Eg: isotopes 17Cl35, 17Cl37.
(ii) Atoms of different elements may have the same atomic masses.
Eg: Isobars 18Ar40, 20Ca40.
(iv) Atoms of one element can be transmuted into atoms of other elements. An atom is no longer indestructible.
(v) Atoms may not always combine in a simple whole-number ratio.
Eg: Glucose C6H12O6 C : H : O = 6 : 12 : 6 or 1 : 2 : 1.
(vi) Atom is the smallest particle that takes part in a chemical reaction.
(vii) The mass of an atom can be converted into energy (E = mc²).
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