Answer: B. Mass number minus atomic number
Explanation: The atomic # is equal to the # of protons. The mass number is the total mass of neutrons & protons. You subtract the protons (atomic number) from the mass of the atom, the formula would be as shown:
Mass - Protons = Neutrons
An example is shown below
Element: Tin
Name shown on periodic table: Sn
Atomic #: 50
Mass # 118.711
118.711 - 50 = 68.711 <--- answer
Mass^ ^Protons/ Atomic #
I hope this helps :)
