Chapter 3, Problem 53P

Interpretation Introduction

Interpretation:

To explain the reason why oxygen has two bonds and two unshared pair of electrons in covalent compounds.

Concept Introduction:

A covalent bond is formed by sharing of same number of electrons between two atoms to complete their octet. Atoms taking part in covalent bond formation may share one, two or three electron pairs thus forming single, double and triple bond respectively.

Lewis structure of a molecule can be determined as-

1. Calculate the total number of valence electrons.(T.V.E. = a).

Sum up all the electrons of all atoms present in the molecule.

If the molecule is an anion, add the same number of electrons as the charge present on the ion.

If it is a cation, subtract the same number of electrons as the charge present on the ion.

2. Calculate the total number of electrons required for each atom to have a complete octet or doublet for hydrogen (b).

3. Therefore number of bonds formed = $\frac{b-\text{a}}{2}$

4. Remaining electrons are called as lone pairs.

5. Assign formal charges to atoms.