Final answer:
The full electron configuration for P^-3 is 1s^2 2s^2 2p^6 3s^2 3p^6.
Step-by-step explanation:
A phosphorus atom has the electron configuration 1s²2s²2p&sup6;3s²3p³. The negative ion P&sup-3 can be obtained by adding three extra electrons, which will occupy the 3p subshell. The full electron configuration for P&sup-3 is 1s²2s²2p&sup6;3s²3p&sup6;.