Answer:
3 P atoms
Step-by-step explanation:
Al₂P₃ => contains 2 Aluminum ions (2Al⁺³) and 3 Phosphide ions (3P⁻³) ... The ions (charged particles) are from atoms that have lost or gained electrons during the bonding process. So, Al₂P₃ => P⁻³ ions from 3 P atoms.