Mon February 21, 2011 By: Sai Ganesh Behara

how do we determine the electron density regions? And why is the no.of electron density regions of triodide anion 5 pls explain

Expert Reply
Mon February 21, 2011

Dear Student


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

if ne denotes the electron density and na the atomic density then :

ne= z na

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.



We hope that clarifies your query.
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