atomic mass is determined by the sum of protons and neutrons numbers in an atom
phosphorus_atom is atom. atomic_mass is not mass. equivalent is atomic_mass. hydrogen_maser_atomic_clock is atomic_clock. neutrons has about_as_much_mass_as_protons rutherford_atom is atomic_theory. atomic_mass_unit is mass_unit. atomic_mass is mass. atoms has mass nickel_atom is atom.