Chapter 9, Problem 14STP

Interpretation Introduction

Interpretation: The electronic configuration of ${\text{P}}^{3-}$ needs to be determined. This is to be explained how this configuration is different from the configuration for the neutral of phosphorus.

Concept introduction:

An element's electron configuration determines how its atomic orbitals exchange electrons. Electron configurations of atoms follow a standard representation in which all atomic sub-shells containing electrons are grouped in a series.

Answer to Problem 14STP

Electronic configuration of ${\text{P}}^{3-}$ is ${\text{1s}}^{\text{2}}{\text{2s}}^{\text{2}}{\text{2p}}^{\text{6}}{\text{3s}}^{2}3{\text{p}}^6$. Neutral phosphorus has three electrons in there outermost shell while ${\text{P}}^{3-}$ has six electrons in there outermost shell.

Explanation of Solution

The electronic configuration of P is as follows:

Atomic number of $\text{P=15}$

$\begin{array}{c}{\text{P=1s}}^{\text{2}}{\text{2s}}^{\text{2}}{\text{2p}}^{\text{6}}{\text{3s}}^{2}3{\text{p}}^{\text{3}}\\ =\left[\text{Ne}\right]{\text{3s}}^{2}3{\text{p}}^{\text{3}}\end{array}$

To form ${\text{P}}^{3-}$ ion, it gains three electrons. Therefore, it contains three more electrons in there 3p orbitals. Hence, the electron configuration for ${\text{P}}^{3-}$ become,

$\begin{array}{c}{\text{P}}^{3-}{\text{=1s}}^{\text{2}}{\text{2s}}^{\text{2}}{\text{2p}}^{\text{6}}{\text{3s}}^{2}3{\text{p}}^6\\ =\left[\text{Ne}\right]{\text{3s}}^{2}3{\text{p}}^6\end{array}$

Conclusion

Atomic number of neutral phosphorus is 15 but in ${\text{P}}^{3-}$ ion it becomes 18. Extra three electrons are added in 3p orbitals in ${\text{P}}^{3-}$ and in neutral phosphorus 3p orbitals have 3 electrons.