J-value may be calculated according to the formula:
J = L+S, …, |L-S|
L = 1, S = 1, J = 1+1 = 2
L = 1, S = 0, J = 1 + 0 = 1
L= 1, S = 1, J = |1-1| = 0
For J = 2, L and S are parallel and point in the same direction. It’s the most disadvantageous system, the highest energy.
If J = 1, L and S are perpendicular to each other. Only one of them is thus fruitfully projected on the z-axis.
Antiparallelity of L and S onsets when J = 0. Because the total angular momentum of the electron shell is minimum, this is the ground state with the lowest energy.