Chapter 12.4, Problem 3RQ

Interpretation Introduction

Interpretation:

The reason why molecular structure of some molecules is different from the structure given by arrangement of electron pairs is to be written.

Concept introduction:

To determine the shape of molecule, the total number of bonding and non-bonding pairs is to be calculated for the central atom. Then these are arranged in a shape so that electron- electron repulsions are minimum.

Answer to Problem 3RQ

The molecular structure for a molecule is different from the arrangement of electron pairs when central atom has non- bonding pairs of electrons.

Explanation of Solution

According to VSEPR theory, lone pair-lone pair repulsions are maximum. If in a molecule central atom has lone pair of electrons then its structure will be little different from the structure suggested by arrangement of electron pairs.

Example:

Ammonia has pyramidal shape although it has 4 pairs of electrons around nitrogen.

Conclusion

Thus, if there is presence of non-bonding electrons, the structure will be different from the structure as given by arrangement of electron pairs.