Which factor most influences the strength of dispersion forces?

Which factor most influences the strength of dispersion forces?

• A. Molecular shape
• B. Bond polarity
• C. Molecular size/weight
• D. Phase of matter

Answer: (C)

The strength of dispersion forces is governed by how easily a molecule's electron cloud can be distorted, i.e., its polarizability. Larger or heavier molecules have more electrons and a bigger, more easily distortable electron cloud, which leads to larger instantaneous dipoles and stronger London forces. This is why dispersion forces become more significant as molecular size/weight increases, contributing to higher boiling points for bigger nonpolar molecules. Bond polarity drives dipole-dipole interactions, not the baseline dispersion forces, and while phase of matter affects how closely molecules touch, the intrinsic strength of dispersion forces is set mainly by molecular size/weight.

The strength of dispersion forces is governed by how easily a molecule's electron cloud can be distorted, i.e., its polarizability. Larger or heavier molecules have more electrons and a bigger, more easily distortable electron cloud, which leads to larger instantaneous dipoles and stronger London forces. This is why dispersion forces become more significant as molecular size/weight increases, contributing to higher boiling points for bigger nonpolar molecules. Bond polarity drives dipole-dipole interactions, not the baseline dispersion forces, and while phase of matter affects how closely molecules touch, the intrinsic strength of dispersion forces is set mainly by molecular size/weight.