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Which of the following postulates of Dalton's Atomic Theory was later found to be incorrect based on the discovery of isotopes?

Option: 1

Atoms can combine in fixed ratios to form compounds.


Option: 2

Atoms of different elements have different properties.


Option: 3

Atoms of the same element are identical in mass and other properties.


Option: 4

Atoms are indivisible and indestructible


Answers (1)

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Dalton's Atomic Theory proposed that in same element all atoms are identical in mass and other properties. However, the discovery of isotopes revealed though in same element atoms can have different masses due to the presence of different numbers of neutrons in the nucleus. For example, carbon-12 and carbon-14 are both isotopes of carbon, but they have different masses due to the presence of different numbers of neutrons in their nuclei. Therefore, option C is the correct answer.

Option (1) is incorrect because the postulate that atoms can combine in fixed ratios to form compounds is still a valid part of Dalton's Atomic Theory. Hence option A is incorrect.

Option (2) is incorrect because the postulate that atoms of different elements have different properties is still a valid part of Dalton's Atomic Theory. Hence option B is incorrect.

Option (4) is incorrect because the postulate that atoms are indivisible and indestructible is no longer accepted due to the discovery of subatomic particles and nuclear reactions. However, this postulate was not found to be incorrect specifically based on the discovery of isotopes. Hence option C is incorrect.

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SANGALDEEP SINGH

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