Question

What rule is this: "When filling orbitals of equal energy, electrons fill them singly first with parallel spins"?

Answer 1

`"Hund's rule of maximum multiplicity"`.

Explanation:

You will have to look up the details, but Hund's rule states that in a many electron atom, the ground state is when the spin quantum number is maximized. Of course this means parallel spins. Thus the nitrogen atom should be a paramagnet.