<P> Rhenium is the only metal known to bond with seven fluorides, which is the record for number of charged ligands for a charge - neutral metal compound. Rhenium heptafluoride adopts a pentagonal bipyramid molecular geometry . Calculations shows that the currently unknown but perhaps possible iridium heptafluoride (report of synthesis is being prepared), technetium heptafluoride, and osmium heptafluoride will also have this structure . </P> <P> Osmium octafluoride was first reported in 1913, but in 1958 that compound was shown to be actually osmium hexafluoride . A 1993 theoretical study predicted very weak bonds in osmium octafluoride and said that it would be difficult to ever detect experimentally . The study predicted that, if made, OsF would have Os--F bonds of two different lengths . </P> <P> The nonmetal binary fluorides are volatile compounds . They show a great difference between period 2 and other fluorides . For instance, period 2 elements elements fluorides never exceed the octet in their atoms . (Boron is an exception due to its specific position in the periodic table .) Lower - period elements, however, may form hypervalent molecules, such as phosphorus pentafluoride or sulfur hexafluoride . The reactivity of such species varies greatly--sulfur hexafluoride is inert, while chlorine trifluoride is extremely reactive--but there are some trends based on periodic table locations . </P> <P> Boron trifluoride is a planar molecule . It has only six electrons around the central boron atom (and thus an incomplete octet), but it readily accepts a Lewis base, forming adducts with lone - pair - containing molecules or ions such as ammonia or another fluoride ion which can donate two more electrons to complete the octet . Boron monofluoride is an unstable molecule with an unusual (higher than single) bond to fluorine . The bond order has been described as 1.4 (intermediate between a single and double bond). It is isoelectronic with N . </P>

If there are 5 fluorines and 1 phosphorous atom. what is the formal name