JEE Main · 2019 · 11 Jan 2019 · Shift 2 · Chemical Bonding and Molecular Structure

An electron-deficient hydride is one whose central atom lacks a complete octet. In $\mathrm{B}{}_2\mathrm{H}{}_6$, $\mathrm{GaH}{}_3$ and $\mathrm{AlH}{}_3$ the central atom carries only six electrons and is electron deficient, but in $\mathrm{SiH}{}_4$ silicon has a full octet of eight electrons, so $\mathrm{SiH}{}_4$ is the one that is not electron deficient.