LiF behaves entirely differently. The difference in electronegativity between the two atoms is so great that a diatomic LiF molecule is in a highly unfavorable state. There is a strong tendency for the electron pair to be given over completely to the F atom, thereby turning the molecule into two ions:

(The dots represent outer-shell electrons, and the bond line between atoms represents an electron pair.)

When this occurs, each ion attracts all the ions present, and each attracts every . The gas of separate Li-F molecules condenses into a liquid of and ions (see next paget) when the temperature decreases below 1676°C.

Only above this temperature does LiF have enough energy to force the electron pair back toward the ion and turn the separate ions into gaseous Li-F molecules.