Question

____ are atoms of different elements which have the same number of nucleons but different atomic numbers.

Answer 1

Isobars:

1. The atoms of different elements having the same mass number (or atomic mass) but a different atomic number are called isobars.
2. The mass number of an atom depends upon the number of protons and neutrons, called nucleons.
3. For example, the elements calcium$\left(\mathrm{C}\right)$ and argon $\left(\mathrm{Ar}\right)$ are isobars. Both the elements have 40 as their mass number.

Hence, Isobars are atoms of different elements with the same number of nucleons but different atomic numbers.