Chapter 10, Problem 10.46P

Interpretation Introduction

Interpretation:

Increasing order of $\text{F}-\text{A}-\text{F}$ bond angle in the given ${\text{AF}}_n$ species is to be determined.

Concept introduction:

The following steps are used to determine the molecular shape of the given molecule.

Step 1: Write the Lewis structure of the given formula and place the atoms.

Step 2: Count all electron groups including bonding and non-bonding pairs around the central atom and use it to assign one of the five electron-group arrangement.

Step 3: Write the ideal bond angle related to the electron-group arrangement and the effect of any deviation can be predicted by using VSEPR.

Step 4: Count the bonding and non-bonding electron groups and draw the molecular shape accordingly.

The deviation in the value of ideal angles is directly proportional to the number of lone pair present on the central atom because its presence causes more repulsion between itself and bond pair. In other words, bond pair-bond pair has less repulsion than lone pair-bond pair repulsion and lone pair-lone pair has the most repulsion. Hence deviation from the ideal angle is less or bond angle is more as the number of lone pair decreases on the central atom.