atomic nucleus
core of the atom; composed of bound nucleons (protons and neutrons)
hydron
cationic form of atomic hydrogen (symbol H⁺), informally called "proton"
helion
nucleus of helium, a doubly positively charged helium ion. In practice, helion refers specifically to the nucleus of the helium-3 isotope, consisting of two protons and one neutron.
halo nucleus
core atomic nucleus surrounded by orbiting protons or neutrons