Which particle has a mass that is approximately the same as the mass of a proton?
(1) an alpha particle (3) a neutron
(2) a beta particle (4) a positron
Protons have a mass of 1 Alpha particles are Helium nuclei, so have mass 4 Beta particles are electrons, and so have mass 0 Neutrons have mass 1 Positrons are anti-matter forms of electrons, and so have mass 0 The answer is (3) a neutron
