Question

Which of the following pairs represents isobars?

• A. ${}_{19}{K}^{40}$ and ${}_{11}N{a}^{23}$
• B. ${}_{2}H{e}^3$ and ${}_{2}H{e}^4$
• C. ${}_{12}M{g}^{24}$ and ${}_{12}M{g}^{25}$
• D. ${}_{19}{K}^{40}$ and ${}_{20}C{a}^{40}$

Answer 1

The correct option is D ${}_{19}{K}^{40}$ and ${}_{20}C{a}^{40}$

Isobars are the elements having different atomic number but same mass number. Here, in option D, $K$ and $Ca$ have same mass number. Thus, D is the right answer.