Concept:Isobars are atoms of different elements that share the same mass number but have different atomic numbers. Mass number is the total number of protons and neutrons in the nucleus.
Explanation:- Since isobars belong to different elements, their atomic numbers (number of protons) are different. Hence option A is incorrect.
- In a neutral atom, the number of electrons equals the atomic number. Therefore, electrons also differ among isobars. Option B is wrong.
- Mass number is the same for all isobars, so option C is correct.
- Number of neutrons = mass number − atomic number. Because atomic numbers differ while mass number is constant, neutron counts are different. Option D is incorrect.
Example: Carbon-14 (₆C¹⁴) has 6 protons and 8 neutrons; Nitrogen-14 (₇N¹⁴) has 7 protons and 7 neutrons. Both have mass number 14 but differ in protons and neutrons.
Answer:C. Mass numbers.