atomic mass (noun) mass number: protons and neutrons
Sinonime: ace*, aerialist, aeronaut, aviator, bellwether,
captain, conductor, coxswain, dean,
director, doyen/doyenne, eagle, flier, flyer, guide, helmsperson, jockey, lead, leader, navigator, one at the controls, one at the wheel,
scout*, steerer, steersperson, wheelperson