The principal quantum number (n), ●Quantum Numbers, -part-1

 Quantum numbers : 

the concept of quantum numbers was first introduced by Neils Bohr,

1. principal (n)   2. Azimuthal (l)  3. Magnetic  (m)   4.spin 

Bohr's model predicts only  one quantum number (n), But the quantum mechanical model of atom introduces three more quantum numbers, As a matter of fact, in order to have a complete knowledge of the energy  states of electron in an atom, four quantum numbers are required.  The size and shape of electron  orbits, orientation  of orbitals in the magnetic field  and the spin of an electrons about its own  axis — are all characterized by a thorough knowledge  of the four quantum numbers.

[1.] The principal quantum numbers (n) :

• thus " n "  indicates the size of the electron orbit. 

• The principal quantum number determines  the energy of the electron present in any shell.

 it also indicates how the probability of finding the electron varies with the distance from the nucleus. ( ■ size of orbitals)

                                n  :   1      2      3      4      5

            energy shell  :   K      L     M     N      P

max no. of electron :   2      8      18    32   50

•[no. of electron = 2n² ]