What are Quantum Numbers?
Quantum numbers are basically those numbers which help us in describing the orbital occupied by an electron.
It tells us the following four things:
 The distance of the electron from the nucleus.
 Shape of the orbital
 Position of the orbital
 Spin of an electron
There are four quantum numbers that help us to describe the location and behavior of an electron. They are:

Principal Quantum Number

Angular Quantum Number

Magnetic Quantum Number

Spin Projection Quantum Number
Principal Quantum Number
The first quantum number is the principal quantum number (n) which describes the main energy level and size of an orbital i.e. the distance of the orbital from the nucleus. The principal quantum number is also referred to as a shell and the number of orbital in a shell and is given by n2.
Angular Quantum Number
The second quantum number, named as the azimuthal quantum number and also known as orbital angular momentum, is denoted by l. It describes the shape and the type of orbital. There are 4 types of orbitals i.e. s, p, d, and f. The value of l ranges from 0 to n1.
Magnetic Quantum Number
The third quantum number is the magnetic quantum number which is denoted by m. This describes the spatial orientation of the orbital. The sorbital has only 1 possible position, porbital has 3 possible positions, dorbital has 5 possible positions and forbital has 7 possible positions. The number of possible positions in an orbital is given as 2l + 1.
Spin Projection Quantum Number
The fourth quantum number is the spin quantum number (m_{s}). It deals with the spin of an electron in a subshell about an axis. The spin quantum number describes the intrinsic electronic spin in which +12 denotes the counterclockwise spin of an electron and −12 represents the clockwise spin. The maximum number of electrons in an orbital is two and these two electrons should have opposite spins.
The shape of the sorbital is spherical, porbital is dumbbell shaped. The shapes of d and f orbital are very complex and cannot be determined easily. It has been observed that dorbital are pearshaped.
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