Explain the orbital notation.

Hint: Orbitals are associated with regions around the nucleus of an atom that are highly accessible to electrons or there is a high probability of finding electrons in those spaces. Each orbital is a subshell and can contain a maximum of two electrons in the opposite spins.

Complete answer:
The orbital notation system involves assigning alphabets to different orbitals for their easy identification. These notations are used while writing the electronic configurations of different elements that indicate the number of electrons that present in different orbitals.
The electrons are present in various energy levels called shells that are sequentially filled in the increasing order of energy. Each shell has a fixed number of subshells equal to the azimuthal quantum number which is always less than the principal quantum number. Each subshell contains a fixed number of orbitals that can accommodate a maximum of two electrons that are in opposite spins.
The different subshells and the number of orbitals that they contain can be written as follows:
 $ l = 1{\text{ }}s{\text{ - orbital (1 orbital)}} $
 $ l = 2{\text{ }}p{\text{ - orbital(3 orbitals)}} $
 $ l = 3{\text{ }}d{\text{ - orbital(5 orbitals)}} $
 $ \Rightarrow $ Thus, $ {\text{s,p,d,f}} $ are the different alphabetical notations assigned to orbitals depending on the value of the azimuthal quantum number.
The electronic configurations are written in the following manner:
 $ n{s^x}n{p^y}n{p^z} $ where $ n = {\text{energy level}} $ and $ x,y,z = {\text{number of electrons in each orbital}} $ .

Note:
If an orbital contains two electrons that have to be paired in nature and if it contains a single electron then it has to be unpaired. The different orbitals have different shapes like spherical, dumbbell shaped and double dumbbell shaped.