Chapter 9, Problem 9.82P

Interpretation Introduction

Interpretation:

The reason for the shorter bond length of $\text{HF}$ compared to the covalent radii of hydrogen and fluorine is to be determined. Also, the reason for the decrease in the difference in the bond length down the group is to be explained.

Concept introduction:

Electronegativity is the tendency of an atom to attract the shared electrons in the bond towards itself. The more electronegative atom will more attract the bonding electrons towards itself than the less electronegative atom. Therefore the electrons will spend more time with the more electronegative atom than an electropositive atom. The electronegative atom will acquire the partial negative charge and the electropositive atom will acquire a partial positive charge. The polarity is represented by an arrow towards the more electronegative element.

Here, B is the electronegative atom and A is the electropositive atom.

Bond polarity and ionic character can be estimated by $\Delta \text{EN}$. $\Delta \text{EN}$ is the electronegativity difference between the atoms bonded to each other. The formula to calculate $\Delta \text{EN}$ in AB bond is as follows:

$\Delta \text{EN}=\left(\text{electronegativity of B}\right)-\left(\text{electronegativity of A}\right)$

Here, B is the electronegative atom and A is the electropositive atom.