alleryIsotopes of an element differ in:
ANumber of protons
BNumber of electrons
CNumber of neutrons
DAtomic number
Answer & Solution
Correct answer: C. Number of neutrons
1. Isotopes of an element have the SAME atomic number (Z = protons).
2. They differ only in mass number A — i.e., the number of NEUTRONS (A − Z).
3. Example: ¹H, ²H (deuterium), ³H (tritium) — all hydrogen, A = 1, 2, 3.
_Source: syllabus Chem Ch 2 §2.1 Atomic and Mass Numbers_
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