What are electron deficient compounds? Are `BCl_3` and `SiCl_4` electron deficient?

Answer

Molecules in which the central atom is short of eight electrons in the valence shell are called electron deficient molecules. `BCl_3` is electron deficient as B contains only 6 electrons in the valence shell. `SiCl_4` is not electron deficient because Si has 8 electrons in its valence shell.