A yellow metallic powder is burnt in a stream of fluorine to obtain a colourless gas X which is thermally stable and chemically inert. Its molecule has octahedral geometry. Another colourless gas Y with same constituent atoms as that of X is obtained when sulphur dichloride is heated with sodium fluoride. Its molecule has triangular pyramidal structure X and Y are
SF4 has trigonal pyramidal shape due to sp3d hybridisation. SF6 is octahedral due to sp3d2 hybridisation. Sulphur has S8 molecular geometry