The distribution of electrons in orbit or orbital is called electronic configuration.
Following are the rules which help to write the electronic configuration of any element.
According to Aufbau principle:
“Electrons are filled in the orbital w. r. t to increasing energy levels. i.e.
1s², 2s², 2p6, 3s², 3p6, 4s², 4p6, 3d10, 4p6
Electrons should be filled in that orbital as it has lowest value of (n +I). Here
n = principle quantum number
l = azimuthal quantum number
Electrons are filled in the orbital in separate orbital with parallel spin instead of same orbital with opposite spin.
(2l + 1) RULE:
It is used to determine the maximum orientation of each orbital e.g.
l = 0 —– s 2(0) + 1 = 1
l = 1 —– p 2(1)+1 = 3 (px, py, pz)
2(2l + 1) RULE:
It is used to determine the maximum capacity of each orbital. E.g.
l = 0 —– s 2[(2)(0) + 1] = 2
l = 1 —– p 2[(2)(1) + 1] = 6
The half of bond length of a molecule consist of two similar atoms is called Atomic Radius. E.g. the bond length of C – C is 1.54°A and its radius is 0.77°A, half of 1.54° A.