What are weak forces resulting from temporary shifts in electron density called?

The forces that arise from temporary shifts in electron density are known as London dispersion forces. These forces occur due to the momentary uneven distribution of electrons in a molecule, which creates a temporary dipole. As a result, these temporary dipoles can induce dipoles in neighboring molecules, leading to a weak attraction between them. This phenomenon is particularly significant in nonpolar molecules, which do not have permanent dipoles.

London dispersion forces are typically the weakest type of intermolecular force, but they are present in all molecules, regardless of whether they are polar or nonpolar. They become more substantial as the size of the molecule increases because larger molecules have more electrons, leading to greater fluctuations in electron density.

In contrast, covalent bonds involve the sharing of electrons between atoms, and dipole-dipole forces arise from interactions between the positive end of one polar molecule and the negative end of another. Hydrogen bonds are a specific type of dipole-dipole interaction that occurs when hydrogen is bonded to highly electronegative atoms like fluorine, oxygen, or nitrogen. Each of these other forces operates on different principles than the temporary interactions described by London dispersion forces.