Electron subshell
In atomic physics, an electron subshell is a group of atomic orbitals with the same values of the principal quantum number n and the angular momentum quantum number l. Multiple subshells comprise an electron shell. Subshells are identified by the letters s, p, d, f, g, h, etc, corresponding to the l-values 0, 1, 2, 3, 4, 5, etc.
The names 's', 'p', 'd', and 'f' originate from a now-discredited system of categorizing spectral lines as "sharp", "principal", "diffuse", or "fundamental", based on their observed fine structure. When the first four types of orbitals were described, they were associated with these spectral line types, but there were no other names. The designations 'g' and 'h' were derived by following alphabetical order.