Which of the following pair of nuclei are isobars of the element?
- 31H and 32He
- 19880Hg and 19779Au
- 21H and 31H
- 23692U and 23892U
Answer
(1) 31H and 32He
Solution
Isobars have the same mass number A but different atomic numbers Z.
(1) 31H, 32He: A = 3 for both, Z different isobars
(2) A = 198 and 197 not isobars (they have the same number of neutrons, 118: isotones)
(3) and (4): same Z, different A isotopes
Answer: (1)