Hello. Here, I'm asking why total orbital quantum number l and total magnetic quantum number m are zero for closed subshell in atom. Let me review the addition of angular momentum first: Each electron has its own orbital quantum number li and magnetic quantum number mi. Then for two electrons, total magnetic quantum number is obviously m = m1 + m2. Total orbital quantum number l has possibilities of l = l1 + l2, l1 + l2 - 1, ... , |l1 - l2|. This rule can extends for more electrons. In return to closed subshell problem, m should be zero as summation of all individual mi in closed subshell is zero. However, l has several possibility according to rule above. For example, for p (li = 1) subshell, l = 2, 1, 0. Obviously total l can have non-zero value. How is total l for closed subshell zero as literature says? And in case of two electrons in p subshell which have m1 = 1 and m2 = 0 (unfilled subshell), m = 1 and l = 2,1,0. Does it mean that there are several possibilities of term symbol to these electronic configuration?