Answer:
1 Proton
Step-by-step explanation:
Hydrogen (H) atoms have 1 proton. Hydrogen atoms with 1 proton and 1 electron are neutral hydrogen (1H1). Hydrogen atoms with 1 proton, 1 electron, and 1 neutron are a heavy isotope of hydrogen called deuterium (2H1). If a proton is added to hydrogen, we then have a different element - helium (4He2)