posted by Arora
Which one is more stable, [PCl4]+ or [PCl6]- ? Why?
I'm thinking it has something to do with the fact that the former is tetrahedral and the latter is octahedral, but I'm not sure. Does that affect stability?
[PCl4]^+ is sp3 which is a tetragedral shape; however, note that the electrons fit exactly; i.e., P = 5 and 4*7 = 28 for Cl for total of 33 for PCl4 or 32 for [PCl4]^+.
For PCl6, it is octahedral which is d2sp3; however, adding an electron to make it [PCl6]^- adds an extra electron to an already filled d2sp3 and it really has no place to go. So I think the latter is less stable.
See this site.