atomic mass is determined by the sum of protons and neutrons numbers in an atom
atomic_nucleus is microscopic_object. rutherford_atom is atomic_theory. equivalent is atomic_mass. phosphorus_atom is atom. atomic_mass_unit is mass_unit. neutrons has about_as_much_mass_as_protons atoms has mass nickel_atom is atom. hydrogen_maser_atomic_clock is atomic_clock. atomic_mass is mass.