# Why is Helium ground state a singlet?

I see that in the 1$s$ orbital the electrons have to have different spins, still there is two possible states,

• a singlet state with an anti-symmetric superposition of spins and symmetric spatial part
• a triplet state with symmetric superposition of spins and anti-symmetric spatial part

So, the question reduces to WHY the first one? I have read somewhere else that a ground state has to have a symmetric spatial wave function always but without further reasoning why this should be necessarily true.

• Well if there is no a priori reason for the ground state to have a symmetric spatial wave function than how can we know its the symmetric one? Is this something we know from spectroscopy where we see that $\Delta s = 0$ selection rule should only yield transitions from singulets? – Marsl Feb 15 '17 at 18:05