Which of the following substances exhibit ONLY dispersion forces?

Which of the following substances exhibit ONLY dispersion forces?

(a) Xe

(b) O2

(c) OCl2

(d) BCl3

Answer: a. Xe

London dispersion forces, or simply, dispersions force is a form of intermolecular power that exists between all molecules. They are caused by short-lived dipoles that result from an unbalanced distribution of electrons within the molecule.

Out of the given options, Xe (xenon) is characterized by dispersion forces only. Xe is a noble gas, indicating that its atoms have fully filled valence electron shells. Noble gases are not involved in hydrogen bonding or dipole-dipole interactions. The intermolecular force between Xe atoms is dispersion forces only.

O2 (oxygen) shows a small amount of dispersion forces, but it may engage in dipole-dipole interactions. The O2 molecules have minor partial charges and are able to interact through aligned dipoles.

Dispersion forces are evident in OCl₂ (dichloride monoxide) and BCl₃ (Boron dichloride); however, the molecules contribute to dipole-dipole interactions based on their structure. Orthoclase is a bent molecular geometry and uneven distribution of electronegativity with permanent dipole moment. BCl₃ possesses a trigonal planar molecular geometry with an enormous partial negative charge on its chlorine atom to capture dipole-dipole interactions .

In conclusion, Xe is the lone substance that manifests dispersion forces only and does not have dipole-dipole interactions or hydrogen bonding. Being a noble gas, due to the structure of Xe atoms no interaction can be observed beyond instantaneous dipole-induced dipole attraction.