An atom's mass number is composed of the total number of contained in an atom.?

An atom's mass number is composed of the total number of protons and neutrons found in its nucleus. Protons are positively charged particles, while neutrons are neutral. The mass number provides an indication of the Atomic Mass and helps distinguish between different isotopes of an element. Electrons, which are negatively charged, are not included in the mass number as they have negligible mass compared to protons and neutrons.