Question

explain quantum no. give notes also

Answer 1

Answer :

Quantum mechanics:

The branch of science that deals with the dual behaviour of matter is called quantum mechanics.

It was developed by Werner Heisenberg and Erwin Schrödinger in 1926.

Quantum numbers :

Orbitals are distinguished on the basis of their size, shape and orientation.

Each of the atomic orbital is designated by three quantum numbers i.e.,

$n \: , \: l \: and \: m1$

》Principal quantum number 'n'

This determines the size and energy of the orbital. Also it is equivalent to the number of shell.

$\: \: \: \: \: \: \: n = 1 \: 2 \: 3 \: 4 \\ shell = K \: L \: M \: N$

》Azimuthul quantum number 'l' :

It is also known as subsidiary quantum number or orbital angular momentum. It's value ranges from 0 to (n-1).

For sub-shell s the value of 'l' will be 0 and so on.

$value \: of \: l \: \: \: = 0 \: 1 \: 2 \: 3 \: 4 \: 5........ \\ sub - shell = s \: p \: d \: f \: g \: h........$

》Magnetic orbital quantum number 'm' :

It gives information about the orientation of orbital with respect to co-ordinate axis. For any sub-shell, it's value is (2l+1).

$value \: of \: l \: \: \: = 0 \: 1 \: 2 \: 3 \: 4 \: 5 \\ sub - shell = s \: p \: d \: f \: g \: h \\ orbital \: no. = 1 \: 3 \: 5 \: 7 \: 9 \: 11$

》Electron spin quantum number :

An additional quantum number was proposed by George Uhlenbeck and Samuel Goudsmit in 1925 named as electron spin quantum number ms.

It can take values of :

$+ \frac{1}{2} \: and \: - \frac{1}{2}$

They both have opposite spins i.e., spin up (⬆) and spin down (⬇) .