Aluminium and phosphorus are close to one another in the Periodic Table but the P3 - ion is much larger than the Al3 + ion. Explain the reason for this change in size.

The P" ion has an electh arrangement of 2,8,8 ie three filled

electron energy level: The AP' ion has on electron

arrangement of 2,8 ie two filled electron energy levels. The

third electron energy level is further away from the nucleus

than the second and so the P" ion is the larger ion