1. Pauli Principle: The total WF must be antisymmetric w. r
Pauli Principle: The total WF must be antisymmetric w.r. to exchange of two electrons  a singlet state has symmetric spatial, antisymmetric spin function, triplet vice versa.
Pauli Exclusion Principle: No two e- can have the same set of quantum numbers.

2. L-S coupling in multielectron atoms:
Every electron has angular momentum
and spin .
Define
”total orbital angular momentum”
The individual
but in the absence of spin-orbit interaction for each electron, the total angular momentum is conserved! That means we can label the states by the quantum number L
Define:
Define
”total spin” → label with quantum number S
”total angular momentum”
→ label with quantum number J = |L+S| ... |L-S| in steps of 1
Levels of the same L are called terms and are described by a capital letter: S, P, D, F, ...
MJ (z-projection of J) can have values between –J and +J in steps of 1
Unsöld’s Theorem: Full shells and subshells have L = 0, S = e.g. L(1s2) = 0; L(2p6) = 0
Atomic term symbols: 2S+1LJ