give reason:
SiF6^2- exists while CF6^2- does not.
Carbon does not form CF62- because it does not have any vacant d orbital of lower energy and hence it is unable to accept lone pair of electron in order to form CF62-.
Moreover the size of carbon is so small that it is unable to accommodate 6 fluorine atoms. However, silicon on the other hand has vacant 3d orbital of lower energy which can be used to expand its valency. Therefore SiF62- thus formed is stable and exist in nature.
Moreover the size of carbon is so small that it is unable to accommodate 6 fluorine atoms. However, silicon on the other hand has vacant 3d orbital of lower energy which can be used to expand its valency. Therefore SiF62- thus formed is stable and exist in nature.