Question

Which of the following pairs are isobars ?

(i) ${}_{26}{}^{58}\mathrm{A}$, ${}_{28}{}^{58}\mathrm{B}$

(ii) ${}_{35}{}^{79}\mathrm{X}$, ${}_{35}{}^{80}\mathrm{Y}$

Give reasons for your choice.

Answer 1

${}_{26}{}^{58}\mathrm{A}$ and ${}_{28}{}^{58}\mathrm{B}$ are isobars because they have same number of nucleons i.e. their mass numbers are same but atomic number is different.