Question

Which is a pair of isobars?

विकल्प

• \({ }_{20}^{40} \mathrm{Ca}\) and \({ }_{18}^{40} \mathrm{Ar}\)

• \({ }_{1}^{1} \mathrm{H}\) and \({ }_{1}^{3} \mathrm{H}\)

• \[ {}^{16}_{\phantom{1}8}\mathrm{O} \text{ and } {}^{17}_{\phantom{1}8}\mathrm{O} \]

• \({ }_{11}^{23} \mathrm{Na}\) and \({ }_{11}^{24} \mathrm{Na}\)

Answer 1

\({ }_{20}^{40} \mathrm{Ca}\) and \({ }_{18}^{40} \mathrm{Ar}\)

Explanation:

\({ }_{20}^{40} \mathrm{Ca}\) has Z = 20 whereas \({ }_{18}^{40} \mathrm{Ar}\) has Z = 18.

Both have mass number A = 40, so they are isobars.

The other pairs have the same Z but different A, so they are isotopes.