What do you understand by 

(i) electron rich – compounds of hydrogen, 

(ii) electron-precise, and 

(iii) electron-deficient? Provide justification with suitable examples.

Asked by Abhisek | 1 year ago |  134

1 Answer

Solution :-

Molecular hydride is classified on the basis of the presence of the bonds and total number of electrons in their Lewis structures as:

  1. Electron-deficient hydrides
  2. Electron-precise hydrides
  3. Electron-rich hydrides

An electron-deficient hydride has very less electrons, less than that required for representing its conventional Lewis structure.


Diborane (B2 H6)

In B2 H6, there are 6 bonds in all, out of which only 4 bonds are regular 2 centered-2 electron bonds.

The remaining 2 bonds are 3 centered-2 electron bonds i.e., 2 electrons are shared by 3 atoms. Hence, its conventional Lewis structure cannot be drawn.

By conventional Lewis structure, an electron-precise hydride has a sufficient number of electrons to be represented.

 e.g. CH4

The Lewis structure can be written as:

4 regular bonds are formed where 2 electrons are shared by 2 atoms. An electron-rich hydride contains excess electrons as lone pairs.

 e.g. NH3

There are 3 regular bonds in all with a lone pair of electrons on the nitrogen atom.

Answered by Pragya Singh | 1 year ago

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