Question

how do you calculate the mass number of an atom?
mass number = # neutrons + # electrons
mass number = # protons + # neutrons
mass number = # protons - # neutrons
mass number = # protons + # electrons

Explanation:

The mass number of an atom is determined by the sum of the number of protons and neutrons in its nucleus. Electrons have negligible mass compared to protons and neutrons and are not included in the mass - number calculation.

Answer:

B. Mass number = # protons + # neutrons