 Polysilicon dihalides (perhalo-polysilenes) have the general formula (Si"X"2)n while the polysilicon monohalides (perhalo-polysilynes) have the formula (Si"X")"n", where "X" is F, Cl, Br, or I and "n" is the number of monomer units in the polymer.The polysilicon halides can be considered structural derivatives of the polysilicon hydrides, in which the side-group hydrogen atoms are substituted with halogen atoms.In the monomeric silicon dihalide (aka dihalo-silylene and dihalosilene) molecule, which is analogous to carbene molecules, the silicon atom is divalent (forms two bonds).