# Is the nonbonding orbital of "NH"_3 a p orbital?

Sep 2, 2017

MOSTLY true. The lone pair is in a molecular orbital that is similar to a $p$ orbital because it has significant $p$ orbital characteristics, but it is not in a pure $p$ atomic orbital.

Consider this orbital diagram of ${\text{NH}}_{3}$:

In a sense, I suppose the lone pair is in a $p$-like orbital... How we label it depends on how we treat the atomic orbitals.

• In a hybridized treatment, one would place the nitrogen lone pair in an $s {p}^{3}$ orbital, as seen in the above diagram. In this case, all four orbitals nitrogen uses for bonding are identical, with 75% $p$ character and 25% $s$ character.
• In an unhybridized treatment, one would place the nitrogen lone pair in a molecular orbital with significant $p$ characteristics, and the molecular orbital would primarily belong to the nitrogen.

And in the above molecular orbital diagram, I would be referring to the molecular orbital labeled $2 {a}_{1}$, which you can see involves interactions between more than one orbital.

Therefore, it is not a pure, nonbonding atomic orbital.

Either approach leads to the conclusion that the orbital contains significant $\boldsymbol{p}$ orbital characteristics, but it is not in a pure $p$ orbital because it is not a purely nonbonding orbital.