Question

What is an example of a tetrahedral bent molecule other than water?

Answer 1

`"H"_2"S"` is an easy example. Sulfur is right underneath oxygen in the periodic table, with `Z = 16`.

Since sulfur atom is larger than oxygen atom (it has a new quantum level), the `"H"-"S"` bond length is longer than the `"H"-"O"` bond length. The internuclear distances `vecr` are:

`vecr_("H"-"S") = "133.6 pm"`
`vecr_("H"-"O") = "95.8 pm"`

Thus, the `"H"-"S"` bond is weaker. A weaker bond with a proton (`"H"^(+)`) implies stronger acidity.

Therefore, we can expect `"H"_2"S"` to be a stronger acid than water, and it is. The pKa of water is about `15.7`, whereas the pKa of `"H"_2"S"` is about `7`, which establishes greater acidity for `"H"_2"S"`.