Define isobars.

Isobars -

• The atoms of different elements having different atomic numbers but the same mass number are called isobars.
• Isobars have different numbers of protons as well as electrons but have the same mass number.
• For example- ${}_{18}{}^{40}\mathrm{Ar}\mathrm{and}{}_{20}{}^{40}\mathrm{Ca}$ are isobars because they are atoms of different elements having different atomic numbers of 18 and 20 but the same mass number of 40.