 Beryllium difluoride , BeF2 , is different than the other difluorides . In general , beryllium has a tendency to bond covalently , much more so than the other alkaline earths and its fluoride is partially covalent ( although still more ionic than its other halides ) . BeF2 has many similarities to SiO2 ( quartz ) a mostly covalently bonded network solid . BeF2 has tetrahedrally coordinated metal and forms glasses ( is difficult to crystallize ) . When crystalline , beryllium fluoride has the same room temperature crystal structure as quartz and shares many higher temperature structures also . Beryllium difluoride is very soluble in water , unlike the other alkaline earths . ( Although they are strongly ionic , they do not dissolve because of the especially strong lattice energy of the fluorite structure . ) However , BeF2 has much lower electrical conductivity when in solution or when molten than would be expected if it were fully ionic . 
