<Li> S → (\ displaystyle (\ overrightarrow (S))): total spin vector for all electrons (S → = ∑ i s i → (\ displaystyle (\ overrightarrow (S)) = \ sum _ (i) (\ overrightarrow (s_ (i))))). </Li> <Li> J → (\ displaystyle (\ overrightarrow (J))): total angular momentum vector for all electrons . The way the angular momenta are combined to form J → (\ displaystyle (\ overrightarrow (J))) depends on the coupling scheme: J → = L → + S → (\ displaystyle (\ overrightarrow (J)) = (\ overrightarrow (L)) + (\ overrightarrow (S))) for LS coupling, J → = ∑ i j i → (\ displaystyle (\ overrightarrow (J)) = \ sum _ (i) (\ overrightarrow (j_ (i)))) for jj coupling, etc . </Li> <Li> A quantum number corresponding to the magnitude of a vector is a letter without an arrow (ex: l is the orbital angular momentum quantum number for l → (\ displaystyle (\ overrightarrow (l))) and l ^ 2 l, m,...⟩ = ħ 2 l (l + 1) l, m,...⟩ (\ displaystyle ((\ hat (l)) ^ (2)) \ left l, m, \ ldots \ right \ rangle = ((\ hbar) ^ (2)) l \ left (l + 1 \ right) \ left l, m, \ ldots \ right \ rangle)) </Li> <Li> The parameter called multiplicity represents the number of possible values of the total angular momentum quantum number J for certain conditions . </Li>

An atom of si and an atom of s have the same number of unpaired electrons