QUANTUM NUMBERS-PRINCIPLE QUANTUM NUMBER-AZIMUTHAL QUANTUM NUMBER-MAGNETIC QUANTUM NUMBER-SPIN QUANTUM NUMBER

QUANTUM NUMBERS

For complete description of an orbital in an atom, few constant numbers are necessary. These constant numbers are necessary to describe the position, spin, energy and orientation of an orbital in space. These are the numbers that complete behavior of an electron in an orbital. These numbers are known as quantum numbers.
There are four quantum numbers:

Principle quantum number (n)

Azimuthal quantum number (l)

Magnetic quantum number (m)

Spin quantum number (s)

PRINCIPLE QUANTUM NUMBER

Principle quantum number represents the energy level of an electron. It is denoted by 'n' .The values of principle quantum number are from 1 to n (where n is a positive whole number i.e. n = 1,2,3,4,.........). Principle quantum number also describes the energy of electron. It also describes the size of orbit.

AZIMUTHAL OR SUBSIDIARY QUANTUM NUMBER

Azimuthal quantum number describes the shape of orbital. It is denoted by

. Values of

are from zero to n-1.

For s-orbital

= 0

For p-orbita

= 1

For d-orbital

= 2

For f-orbital

= 3

With the help of the value of azimuthal quantum number we can determine the total number of energy sub levels in a given energy level.

MAGNETIC QUANTUM NUMBER

Magnetic quantum number indicates the orientation of an orbital in space in an applied magnetic field . It is denoted by ‘m’.
Values of ‘m’ are from (-

) to (+

l) through zero.

Orbital	l	m
s	0	0
p	1	-1, 0, +1
d	2	-2, -1, 0, +1, +2
f	3	-3, -2, -1, 0, +1, +2, +3.

SPIN QUANTUM NUMBER

Spin quantum number describes the spin of an electron in an orbital.

It is denoted by ‘s’.

It has only two possible values.

s = +1/2 , S = -1/2

s = +1/2 for clockwise spin.

s = -1/2 for anti-clockwise spin.

An electron spinning clockwise is indicated by () and anti-clockwise by ()

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