Write the charge and full ground-state electron configuration of the monatomic ion most likely to be formed by p. charge: ground-state electron configuration:

The electron configuration for P is 1s²2s²2p⁶3s²3p³

In order for the p orbital to be full, Phosphorus needs to gain 3 electrons. Therefore the charge is - 3.

The ground state would then be 1s²2s²2p⁶3s²3p⁶. The monatomic ion would be Ar.