Electron subshells (or energy sublevels)
An electron subshell is an energy sublevel within an electron shell in which the elctrons all have the same energy.
The number of subshells within a shell is equal to the shell number (n) (I.e., Shell one contains one subshell while shell three contains three subshells).
The subshells are identified by a number and a letter. The number indicates the shell to which the subshell belongs. The letters are s, p, d, and f (all lowercase).
The energy and maximum number of electrons in a subshell within a given shell depends on the type of subshell.
(2e-) (6e-) (10e-) (14e-)