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# Between $\text{NH}_3$ and $\text{PH}_3$, which is a better electron donor and why?

$\begin{array}{1 1} NH_3 \text{ is the better electron donor because the lone pair of electrons occupies the spherical s orbital and is less directional.} \\ NH_3 \text{is the better electron donor because the lone pair of electrons occupies the} sp^3 \text{orbital and is more directional.} \\PH_3 \text{ is the better electron donor because the lone pair of electrons occupies the} sp^3 {orbital and is more directional.} \\ NH_3 \text{is the better electron donor because the lone pair of electrons occupies the spherical s orbital and is less directional.}\end{array}$

Answer: $\text{NH}_3$ is the better electron donor because the lone pair of electrons occupies the $\text{sp}^3$ orbital and is more directional.
The lone pair of electrons occupies the $\text{sp}^3$ orbital formed from the more compact $\text{2s}$ and $\text{2p}$ orbitals as compared to the $\text{3s}$ and $\text{3p}$ oribitals in $\text{PH}_3$