Frequently Asked Question

The Russell-Saunders scheme, also known as the LS coupling scheme, uses spectroscopic terms that are indeed named after the orbitals. The reason for this naming is that the terms describe the total angular momentum of the electrons in an atom, which is determined by the angular momenta of the individual orbitals.
Here's how it works:

L (orbital angular momentum): This value represents the total orbital angular momentum of the electrons in an atom. It's determined by the sum of the individual l (azimuthal) quantum numbers of each electron. The values of L are denoted by letters: S (L=0), P (L=1), D (L=2), F (L=3), G (L=4), and so on. These letters correspond to the same symbols used to denote the orbitals (s, p, d, f, etc.).
S (spin angular momentum): This value represents the total spin angular momentum of the electrons in an atom. It's determined by the sum of the individual spin quantum numbers (s = +1/2 or -1/2) of each electron.
J (total angular momentum): This value represents the total angular momentum of the electrons in an atom, which is the vector sum of L and S.
The spectroscopic term symbols in the Russell-Saunders scheme are written as (2S+1)L_J, where:

(2S+1) is the spin multiplicity.
L is the orbital angular momentum, represented by a letter (S, P, D, F, etc.).
J is the total angular momentum.
For example, a term symbol of ³P₂ indicates that the atom has three electrons with a total spin angular momentum of S = 1 (2S+1 = 3), a total orbital angular momentum of L = 1 (P), and a total angular momentum of J = 2.
Therefore, the terms in the Russell-Saunders scheme are named after the orbitals because they reflect the orbital angular momentum of the electrons within the atom.