17 4.2 Subsidiary quantum number (ℓ)
Each main level is divided into sublevels (subshells) whose energy is determined by ℓ.
- The number of sublevels in a main level = its principal quantum number n.
- The values of ℓ run from 0 to (n − 1).
- The sublevels have the symbols s, p, d, f:
1Sublevel
0
- s
1
- p
2
- d
3
- f
- So level 1 has 1s only; level 2 has 2s, 2p; level 3 has 3s, 3p, 3d; level 4 has 4s, 4p, 4d, 4f.
- Within the same main level the sublevels differ slightly in energy: f > d > p > s.