The mass number of an atom is calculated by adding proton plus neutrons , therefore option (b) is correct.
What do you mean by the mass number of the atom?
An atom’s mass number, also called atomic mass number is the total number of protons and neutrons present in an atomic nucleus.
Protons and neutrons are collectively known as nucleons.
An electron is almost negligible in weight. Thus, the atomic mass of an atom is almost the same as its mass number.
The total number of protons and neutrons present in one atom of an element is known as its mass number.
Mass number = Number of protons + Number of neutrons
The mass number of an atom is calculated by adding proton plus neutrons , hence option (b) is correct.
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