Question

1. mass number equals

a. protons
b. neutrons
c. protons + neutrons
d. weighted average mass of all element’s isotopes

Explanation:

The mass number of an atom is defined as the sum of the number of protons and neutrons in its nucleus. Option a is just protons, option b is just neutrons, and option d refers to atomic mass (weighted average of isotopes' masses), not mass number. So the correct option is c.

Answer:

c. protons + neutrons