sentences: one proton has one atomic mass unit
docs: equivalent is atomic_mass. hydrogen_atoms has one_proton_and_one_electron hydrogen_atom has only_one_electron hydrogen has atomic_number_of_one h is atomic_nucleus. atomic_mass_unit is mass_unit. 1,000_megawatt_plutonium_reactor is tangible_thing. atoms has mass proton is rocket. atomic_mass is mass.