by • 01/08/2013 • GeneralComments (0)333


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


(n+1) RULE:

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.


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