How do you find the geometry of SiH_4 using the VSEPR method?

Dec 30, 2016

There are 4 valence electrons for $S i$, and the 4 valence electrons from $H$. A tetrahedral geometry is described.

Explanation:

Given that silicon has 4 valence electrons, and each hydrogen contributes 1 electron, there are 8 valence electrons, and thus there are 4 electron pairs to be distrbuted around the central silicon atom.

And if there are 4 electron pairs, the geometry is based on a tetrahedron, i.e. each $\angle H - S i - H = {109.5}^{\circ}$.

And thus silane, $S i {H}_{4}$, has a tetrahedral geometry.

Note that you probably know the geometry of methane, $C {H}_{4}$. Because silicon has precisely the same valence orbitals as carbon, the geometry of silane is an analogue.