Subshell: definition in chemistry
Subshell: A set of orbitals within a shell that all have the same shape, labeled s, p, d or f. It is another name for a sublevel.
A shell numbered n contains n subshells, so the first shell has only 1s, while the third has 3s, 3p and 3d. Each subshell type matches a quantum number, l, equal to 0, 1, 2 and 3 for s, p, d and f. The letters come from old descriptions of spectral lines (sharp, principal, diffuse and fundamental), not from the shapes of the orbitals.
Examples
- The third shell — 3s, 3p and 3d subshells
- An s subshell (l = 0) holds up to 2 electrons
- A d subshell (l = 2) holds up to 10 electrons
- 4f — seven orbitals, filled across the lanthanides
On the periodic table
Each block of the table is named after a type of subshell, so an element's block tells you which kind of subshell its outermost electrons are filling.