3 Which subatomic particles make up a majority of the mass of an atom? 1. Protons 2. Electrons 3. Neutrons A 1 only B 1 and 3 only C 3 only D 2 and 3 only
1 and 3 only, electrons are significantly smaller than both neutrons and protons. Neutrons and protons also make up the biggest part of the atom, the nucleus.
