First Atoms

'''Atoms were matter of the universe, without it, there would be no life, nor stars nor planets. The first atoms appeared as helium and possibly hydrogen only.'''

Helium
Helium is known for the stars and is a gas. Among with hydrogen, helium is abundant and because of this, some stars were composed of more helium than hydrogen. There is a helium-3, it's rare but it could be used in the future, found in the Moon, it can be used for energy and possibly can decay further.

Atomic Mass
The atomic mass is consisted of protons and nheutrons which were the 'mass' of the atom, Uranium has the largest nucleus but elements are bigger than Uranium, such mass could be 200 and over. Here, the mass is not the protons and neutrons, I think.