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Which one of the following statements is not correct?

June 1, 2025 by rawan239

Which one of the following statements is not correct?

Atoms of different elements may have same mass numbers

Atoms of an element may have different mass numbers

All the atoms of an element have same number of protons

All the atoms of an element will always have same number of neutrons

This question was previously asked in

UPSC CDS-1 – 2016

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The statement that is not correct is “All the atoms of an element will always have same number of neutrons”.

Atoms of the same element are defined by having the same number of protons (atomic number). However, atoms of the same element can have different numbers of neutrons, which results in different mass numbers. These variants are called isotopes. Therefore, not all atoms of an element have the same number of neutrons.

Atoms of different elements can have the same mass number (isobars) if their sum of protons and neutrons is equal (e.g., ⁴⁰Ar and ⁴⁰Ca). Atoms of the same element always have the same number of protons. Atoms of the same element can have different mass numbers due to varying numbers of neutrons (isotopes).

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