Читать книгу Astrobiology - Charles S. Cockell - Страница 49

Yet another type of van der Waals interaction is one in which neutral atoms can attract one another. The electron distribution, even in neutral atoms and molecules, is never quite evenly spaced out. A charge anisotropy will exist on account of the electrons in orbit around the atom, which, at a snapshot in time, will always be slightly unevenly distributed around the atom (shown greatly exaggerated in Figure 3.13).

Figure 3.13 Charge imbalance (exaggerated here) around an atom results in a small charge distribution in the atom and creates a dipole. This atom can now engage in van der Waals interactions.

This causes a small dipole moment to be established in the atoms or molecules. These dispersion forces or London forces are important for attraction between inert gases (Ne, Ar, etc.) and covalently bonded molecules (H₂, N₂, CH₄, etc.), but exist between all atoms and molecules to some degree.