Animation of the structure of a molecule of xenon fluoride (XeF4). This molecule has a square planar geometry, with four fluorine atoms (green) forming a square around a central xenon atom (blue). The black line shows the angle between the fluorine atoms to be 90 degrees. This geometry is adopted as the xenon atom has two lone pairs of electrons, above and below the plane of the square, that repel the fluorine atoms equally. See clip K004 3559 for the molecule showing these lone pairs, and K004 3550 for the molecule without this bond angle.