Answer:
The answer to your question is 12
Step-by-step explanation:
Data
Number of electrons in Phosphorus 3+ ion
Process
1.- The sign of the number after the name indicates if the element has lost or gained electrons.
If the sign is positive the element has lost electrons
If the sign is negative the element has gained electrons.
2.- Phosphorus atomic number is 15, then the number of electrons in Phosphorus 3+ will be 12, in this example, Phosphorus lost 3 electrons.