What is a mass number?

Mass number:

1. The mass number is defined as the total number of protons and neutrons present in an atom. It is represented by A.
2. $\mathrm{Mass}\mathrm{number}=\mathrm{number}\mathrm{of}\mathrm{protons}+\mathrm{number}\mathrm{of}\mathrm{neutrons}$
3. Thus, the mass number is also known as the nucleon number as it gives the number of nucleons.
4. The mass number is calculated by finding the sum of protons and neutrons that are present in the nucleus of an atom.