Sometime I read that the helium atoms can be considered as boson, but I don't understand why. I know that its nucleous has a spin of 2 (integer) and that its 2 electrons gives the atom a total spin of 3, an integer. But then why isn't hydrogen considered also as a boson? I think it's considered as a fermion, like the electron itself. Why? The total spin of the H atom isn't 1 (thus an integer)? It seems like only the nucleous is the only important thing in deciding whether an atom can be considered as a boson or fermion, why is it so? And if I have a molecule, how do I determine whether it's a boson or fermion? In Wikipedia one can read and also where the enphasis is mine. Can someone explain me when I can call a particle/atom/molecule a boson?