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Mention the postulates and limitations of Dalton's atomic theory. |
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Answer» Solution :The main postulates of Dalton 's atomic theory are : (i)Matter is composed of tiny indivisible particles called atoms . Theycannot be created or destroyedor transformed into atoms of another element. (ii)Atoms of a givenelement are identical in all respects. (iii)Atoms of DIFFERENT elements aredifferent from each other in all respects. (iv)Atoms ofdifferent elements TAKE part in the chemical reaction and combine in a simple integral ratio to FORM compounds. (v) When elements REACT , the atoms may combine in more than one simple whole NUMBER ratio. Dalton 's atomic theory has been contradicted with the advancement of science and modified on the basisof further research and discoveries. Limitations of Dalton 's atomic theory (i)With the discovery ofsubatomic particles , thatis the electron , proton and neutron , it was concluded that atoms can be further divided. (ii)Discoveryofisotopes proved that atoms of the same element may possess different atomic weights, that atomsof same elementsmay not be identical in all respects . forexample isotopes of hydrogen namely , protium`(._(1)H^(1))` deuterium`(._(1)H^(2))` (iii)In some cases , atoms of different elements are found to have same mass number that is atoms of different elements may be identical . For example , calcium and argon are found to have same mass number. |
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