CDS 2020 PYQ with Answer — The elements of which of the following pairs are isobars? 1H 3H 1H 2H

2020 · Q2

The elements of which of the following pairs are isobars? 1H 3H 1H 2H

General KnowledgeChemistry

Aand
Band 1 1 1 1 12C 14C 40Ar 40Ca
Cand
Dand 6 6 18 20

Explanation

Isobars are atoms of different elements that have the same mass number but different atomic numbers. Argon-40 (atomic number 18) and Calcium-40 (atomic number 20) both have mass number 40, so they are isobars. The hydrogen and carbon pairs in the other options are isotopes (same element, different mass numbers), not isobars. Hence the isobar pair is the 40Ar/40Ca pair (D).