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Q31 (CDS-I/2018) Science & Technology › Basic Science (Physics, Chemistry, Biology) › Atomic and nuclear physics Answer Verified

Which one of the following elements will be an isobar of calcium if the atomic number of calcium is 20 and its mass number is 40?

Result
Your answer: —  Â·  Correct: D
Explanation

Isobars are defined as atoms of different elements that possess the same mass number (A) but different atomic numbers (Z) [1]. The mass number is the sum of protons and neutrons in the nucleus. Calcium is given with an atomic number of 20 and a mass number of 40. To find its isobar, we must identify an element with a different number of protons (Z ≠ 20) but the same total mass number (A = 40). Evaluating the options: Option 1 has a mass of 38 (20+18); Option 2 has a mass of 37 (18+19); Option 3 has a mass of 39 (20+19). Option 4 consists of 18 protons and 22 neutrons, which sums to a mass number of 40 (18 + 22 = 40). This specific configuration corresponds to Argon-40, a well-known isobar of Calcium-40.

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