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

1 Answer
Apr 27, 2016

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

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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".