Like atoms are identical in all respects”. This statement of Dalton’s atomic theory is contradicted. What discovery contradicts this?
The Correct Answer and Explanation is:
The statement “Like atoms are identical in all respects” from Dalton’s atomic theory is contradicted by the discovery of isotopes.
Isotopes are atoms of the same element that have the same number of protons but different numbers of neutrons. This means that while they have the same chemical properties (because they have the same electron configuration), they have different physical properties due to differences in mass. The existence of isotopes shows that atoms of the same element are not identical in all respects, as Dalton had originally proposed.
For example, the element carbon exists primarily in two isotopic forms: carbon-12 (with 6 protons and 6 neutrons) and carbon-14 (with 6 protons and 8 neutrons). Both are chemically carbon, but their atomic masses differ, and carbon-14 is radioactive while carbon-12 is stable. This discovery of isotopes was critical in expanding our understanding of atomic structure.
Further advancements, such as the discovery of nuclear reactions and the identification of subatomic particles like neutrons and protons, also challenged Dalton’s model. For instance, atoms are now known to consist of a dense nucleus made of protons and neutrons, surrounded by a cloud of electrons, and these components can vary in different isotopes of the same element.
The existence of isotopes, therefore, directly contradicts the idea that all atoms of an element are identical, demonstrating that even atoms of the same element can have distinct characteristics, especially in terms of mass and nuclear properties.
