Chem Q

Do you refer to sub-shell (semishell??)??

If so, wikipedia has a detailed description:

Shells and subshells

Shells and subshells (also called energy levels and sublevels) are defined by the quantum numbers, not by the distance of its electrons from the nucleus, or even their overall energy. In large atoms, shells above the second shell overlap (see Aufbau principle).

States with the same value of n are related, and said to lie within the same electron shell.
States with the same value of n and also l are said to lie within the same electron subshell, and those electrons having the same n and l are called equivalent electrons.
If the states also share the same value of m, they are said to lie in the same atomic orbital.
Because electrons have only two possible spin states, an atomic orbital cannot contain more than two electrons (Pauli exclusion principle).

A subshell can contain up to 4l+2 electrons; a shell can contain up to 2n² electrons; where n equals the shell number.


Worked example
Here is the electron configuration for a filled fifth shell:

Shell Subshell Orbitals Electrons
n = 5 l = 0 m = 0 → 1 type s orbital → max 2 electrons
l = 1 m = -1, 0, +1 → 3 type p orbitals → max 6 electrons
l = 2 m = -2, -1, 0, +1, +2 → 5 type d orbitals → max 10 electrons
l = 3 m = -3, -2, -1, 0, +1, +2, +3 → 7 type f orbitals → max 14 electrons
l = 4 m = -4, -3 -2, -1, 0, +1, +2, +3, +4 → 9 type g orbitals → max 18 electrons
Total: max 50 electrons

Electrons are in all atoms

This information can be written as 5s2 5p6 5d10 5f14 5g18 (see below for more details on notation).