Chapter 10, Problem 10.79P

Interpretation Introduction

Interpretation:

All possible resonance forms of ${\text{ClO}}_4{}^{-}$ with the most important form of resonance are to be determined and also average bond order is to be calculated

Concept introduction:

To draw the Lewis structure of the molecule following steps are used.

Step 1: Find the central atom and place the other atoms around it. The atom in a compound which has the lowest group number or lowest electronegativity considered as the central atom.

Step 2: Calculate the total number of valence electrons.

Step 3: Connect the other atoms around the central atoms to the central atom with a single bond and lower the value of valence electrons by 2 of every single bond.

Step 4: Allocate the remaining electrons in pairs so that each atom can get 8 electrons.

When bonds in a molecule can be expressed by different Lewis structures then resonance structures are used to depict the bonding in that molecule. These resonance structures have the same placement of atoms but different locations of bonding and lone pairs of electrons also one resonance form can be converted into another by moving lone pairs to bonding positions, and vice versa.

More important resonance structure is selected as follows:

1. Always prefer smaller formal charge over the larger formal charge.

2. Always prefer the different non zero formal charge on adjacent atoms instead of the same non zero formal charge.

3. A more negative formal charge must be located on the most electronegative atom.

Formula to calculate the formal charge of the atom is as follows:

  $\text{Formal}\text{charge}=\left(\begin{array}{l}\text{number}\text{of}\\ \text{valence}\\ \text{electrons}\end{array}\right)-\left(\left(\begin{array}{l}\text{number}\text{of}\\ \text{non-bonding}\\ \text{electrons}\end{array}\right)+\left(\frac{1}{2}\right)\left(\begin{array}{l}\text{number}\text{of}\\ \text{bonding}\\ \text{electrons}\end{array}\right)\right)$        (1)