Question

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

Answer 1

There are 4 valence electrons for `Si`, 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 `/_H-Si-H=109.5^@`.

And thus silane, `SiH_4`, has a tetrahedral geometry.

Note that you probably know the geometry of methane, `CH_4`. Because silicon has precisely the same valence orbitals as carbon, the geometry of silane is an analogue.