CBSE Class 11-science Answered

Dear Student

The electron density is simply deduced from the atomic density as follows :

if n_e denotes the electron density and n_a the atomic density then :

n_e= z n_a

with z being the number of valence electron per atom.

If you want to know the regions of electron density, follow the simple rules:

a) Draw the Lewis structure for the molecule or ion.

b) Count the total number of regions of high electron density (bonding and unshared electron pairs) around the central atom.

(i) Double and triple bonds count as ONE REGION OF HIGH ELECTRON DENSITY.

1. An unpaired electron counts as ONE REGION OF HIGH ELECTRON DENSITY.
2. For molecules or ions that have resonance structures, you may use any one of the resonance structures.

For example:    has 2 regions of high electron density.

  has 4 regions of high electron density.