## Quantum Numbers

### Quantum Numbers

Quantum Numbers are the numbers required to completely specify the position of electrons. In the presence of strong magnetic field (when spin orbit interaction is not considered), the four quantum numbers are:

1) Principal quantum number (n)
2) Orbital angular momentum quantum number (l)

3) Magnetic quantum number (me)
4) Magnetic spin angular momentum quantum number (Ms)

However, when spin orbit interaction is considered, the four quantum numbers are:
1) Principal quantum number (n)
2) Orbital angular momentum quantum number (l)
3) Total angular momentum quantum number (J)
In Detail-

a) Principal quantum number (n)- It can have values 1, 2, 3 ..(n-1).It is associated with size of orbits radius energy levels.

b) Orbital angular momentum quantum number (l)- It can have values 1, 2, 3 ..∞.It is associated with energy levels, shapes etc.
c) Magnetic orbital quantum number (me)- This can have the value from -l to +l through 0. It represents orientation of electrons orbits in the presence of magnetic field.
d) Magnetic spin angular momentum quantum number (Ms) or (s) – Which can have only two values ± h/4π . It represents the direction of spin of electron, clockwise or anticlockwise.

e) Total angular momentum quantum number (J) – Its possible values are J= l±s. It represents total angular momentum of electron.
f) Total angular magnetic quantum number (mj) – This can have the value from -J to +J through 0. It represents total angular momentum of electron in the direction of magnetic field.

### Isotopes

Isotopes of an element are the atoms of the elements which have same atomic number but different atomic weights. Isobars are the atoms of different elements which have the same atomic weight but different atomic numbers. Isotones are the nuclides which contain the same number of neturons.

### Nuclear forces

Nuclear forces are the strongest forces in the nature. They are the forces of attraction amongst the nucleons (n and p) and are responsible for keeping them together in spite of electrostatic forces of repulsion between protons. Nuclear forces are confined within the nucleus. They are 1038 times stronger than electrostatic forces.

### Nuclear holocaust

It is wide scale devastation caused by nuclear weapons. To save life on earth, nuclear energy should be used for peaceful purposes.