Question

the mass number is equal to: the number of neutrons in an atom the number of electrons in an atom the sum of protons and neutrons in an atom the number of protons in an atom

Explanation:

The mass number of an atom is defined as the sum of the number of protons and neutrons in the nucleus of the atom. Protons and neutrons are the massive particles in the nucleus and contribute to the mass of the atom.

Answer:

C. the sum of protons and neutrons in an atom