Match List-I with List-II.
| List-I (Pair of nuclides) | List-II (Feature of the pair) |
|---|---|
| (A) \({}^{2}_{1}\mathrm{H}\) and \({}^{3}_{1}\mathrm{H}\) | (I) Same number of neutrons |
| (B) \({}^{3}_{1}\mathrm{H}\) and \({}^{3}_{2}\mathrm{He}\) | (II) Same number of protons |
| (C) \({}^{37}_{17}\mathrm{Cl}\) and \({}^{39}_{19}\mathrm{K}\) | (III) Equal numbers of protons and neutrons in each nuclide |
| (D) \({}^{12}_{6}\mathrm{C}\) and \({}^{16}_{8}\mathrm{O}\) | (IV) Same mass number |
Choose the correct answer from the options given below:
Answer & explanation
Correct answer: option 3
The correct answer is Option (3) → (A)-(II), (B)-(IV), (C)-(I), (D)-(III)
(A) \( {}^{2}_{1}\mathrm{H} \) and \( {}^{3}_{1}\mathrm{H} \) — This matches (II) same number of protons. Both have \( Z=1 \). They are deuterium and tritium, two isotopes of hydrogen with 1 and 2 neutrons.
(B) \( {}^{3}_{1}\mathrm{H} \) and \( {}^{3}_{2}\mathrm{He} \) — This matches (IV) same mass number. Both have \( A=3 \), so they are isobars. Their proton numbers are 1 and 2.
(C) \( {}^{37}_{17}\mathrm{Cl} \) and \( {}^{39}_{19}\mathrm{K} \) — This matches (I) same number of neutrons. Chlorine-37 has \( 37-17=20 \) neutrons and potassium-39 has \( 39-19=20 \). They are isotones.
(D) \( {}^{12}_{6}\mathrm{C} \) and \( {}^{16}_{8}\mathrm{O} \) — This matches (III) equal numbers of protons and neutrons in each nuclide. Carbon-12 has 6 protons and 6 neutrons. Oxygen-16 has 8 of each. The two nuclides have different Z, N and A.
NCERT (2026-27):
Atomic Masses and Composition of Nucleus – “… The nuclei of isotopes of a given element contain the same number of protons, but differ from each other in their number of neutrons. …”
Atomic Masses and Composition of Nucleus – “All nuclides with same mass number A are called isobars. For example, the nuclides 31H and 32He are isobars. …”
Atomic Masses and Composition of Nucleus – “… Nuclides with same neutron number N but different atomic number Z, for example 19880Hg and 19779Au, are called isotones.”
Atomic Masses and Composition of Nucleus – “… N - neutron number = number of neutrons … A - mass number = Z + N = total number of protons and neutrons …”