The mass number of an atom is equal to ______.

• the sum of electrons plus neutrons in the atom

• the number of protons, neutrons, and electrons in an atom

• the sum of the protons plus neutrons in the atom

• the number of electrons times the mass of an electron

Respuesta :

the protons and neutrons
I think
the 3rd one...  the sum of the protons plus neutrons in the atom...
hope this helps and HAGD!