Question

Arrange the following covalent diatomic molecules in order of the lengths of the bonds: BrCl, ClF, IBr. Which of these three has the weakest bond (the smallest bond energy)?

Short answer

IBr has the weakest bond and thus has smallest bond energy.

Step-by-step solution

Introduction

Some covalent molecules contain only two atoms, known as covalent-diatomic molecules. They can be homonuclear in which both the atoms are of same element or they can be heteronuclear in which both atoms belong to different elements.

The bond which has the highest bond length is the weakest one and has the lowest bond energy.

Explanation:

Out of these three given molecules, IBr has the weakest bond and thus has smallest bond energy.

Diatomic molecules having larger atoms bonded to each other cannot overlap sidewise ( p orbital overlapping) because p orbitals in them get farther away from each other, so larger atoms do not bond strongly and thus require low energy to be broken which is known as bond energy ( energy required to dissociate a bond). In the molecules given I and Br are the largest so bonding between them will be weakest and thus IBr will have least bond energy.