Question

Is the lone pair of electrons on the nitrogen atom in the ammonia molecule stereochemically inactive?

Answer 1

Nope...........

Explanation:

The ammonia molecule has a lone pair of electrons centred on the nitrogen atom, but ALL of the `3xxN-H` bonds are electron-precise `sigma "-bonds"` formed between `dotH` and the nitrogen atom. The remaining 2 electrons on the nitrogen atom comprise a stereochemically active lone pair.....and this lone pair also rationalizes the basicity of the ammonia molecule....

`OH_2 + :NH_3rightleftharpoonsNH_4^+ + HO^(-)`

And to a first approximation ELECTRONIC geometry around nitrogen is tetrahedral. But MOLECULAR geometry is pyramidal.

On the other hand, the nitrogen atom of the ammonium ion is said to be QUATERNIZED `("ammonium"-=NH_4^+)`; that is the nitrogen lone pair forms a so-called `"coordinate covalent bond"` or `"dative"` or `"donative bond"` to the protium ion.......In `"ammonium ion"`, ALL of the `4xxN-H` bonds ARE EQUIVALENT.