Molecular shape depends on the number of electron pairs around the central atom. Electrons are negatively charged and so each of the electron pairs will repel each other. Lone pairs tend to repel more than bonding pairs and so try to sit position themselves as far away as possible from each other.Start by working out how many electron pairs there are: Xe has 8 outer electrons F has 1 bonding electron, so the four F contribute 4 electrons Total electrons = 12 Electron pairs = 6 Four of the electron pairs are used in bonding between Xe and F, leaving two sets of lone pairs. The lone pairs will sit opposite each other, leaving the Fs to form a square planar shape.