Match List-I (Elements) with List-II (Category).LIST-I(Elements)LIST-…

The correct answer is Option (1) → A-III, B-IV, C-II, D-I

Nuclides are grouped by what they have in common: isotopes have the same Z, isobars the same A, and isotones the same number of neutrons \( N = A-Z \).

(A) \( {}^{238}_{92}\mathrm{U}\,;\,{}^{236}_{92}\mathrm{U} \) — this matches (III) Radionuclides isotopes. Both have Z = 92, so they are isotopes, and both are radioactive, so they are radioactive isotopes.

(B) \( {}^{58}_{26}\mathrm{Fe}\,;\,{}^{58}_{27}\mathrm{Ni} \) — this matches (IV) Isobars. Same mass number A = 58, different Z.

(C) \( {}^{16}_{8}\mathrm{O}\,;\,{}^{17}_{8}\mathrm{O}\,;\,{}^{18}_{8}\mathrm{O} \) — this matches (II) Isotopes. All have Z = 8 with A = 16, 17, 18; all three are stable.

(D) \( {}^{14}_{6}\mathrm{C}\,;\,{}^{15}_{7}\mathrm{N} \) — this matches (I) Isotones. Both contain the same number of neutrons:

    \( N(\mathrm{C}) = 14-6 = 8 \)
    \( N(\mathrm{N}) = 15-7 = 8 \)

Note: Item A, \( {}^{238}_{92}\mathrm{U} \) and \( {}^{236}_{92}\mathrm{U} \), fits both (II) Isotopes and (III) Radionuclides isotopes, since the two nuclides are isotopes and are both radioactive. The question can still be solved because items B and D have only one possible match (isobars and isotones) and Option (1) is the only option containing B-IV and D-I; it pairs A with III and the stable oxygen isotopes of C with II.

NCERT (2026-27):
Atomic Masses and Composition of Nucleus – “… Such atomic species of the same element differing in mass are called isotopes.”

Atomic Masses and Composition of Nucleus – “… All nuclides with same mass number A are called isobars. For example, the nuclides \( {}^{3}_{1}\mathrm{H} \) and \( {}^{3}_{2}\mathrm{He} \) are isobars. Nuclides with same neutron number N but different atomic number Z, for example \( {}^{198}_{80}\mathrm{Hg} \) and \( {}^{197}_{79}\mathrm{Au} \), are called isotones.”