Atoms of different elements with different atomic numbers, having same mass number is known as _________.

Isobars

The correct answer is option 1. Isobars.

Atoms of different elements with different atomic numbers but the same mass number are known as isobars.

Isobars are atoms of different elements that have the same mass number but different atomic numbers. They have the same total number of nucleons (protons and neutrons) but different numbers of protons, which determine their chemical properties and identity as distinct elements.