Final answer:
The ground-state electron configuration of p³⁻ is 1s² 2s² 2p³.
Step-by-step explanation:
The ground-state electron configuration of p³− is 1s² 2s² 2p³. To write the electron configuration, start by filling the lower energy levels before moving to higher energy levels. The 1s orbital can hold a maximum of 2 electrons, the 2s orbital can hold a maximum of 2 electrons, and the 2p orbital can hold a maximum of 6 electrons. Since the phosphorus ion is negatively charged, it gains 3 extra electrons, resulting in a total of 8 electrons in its outermost shell.