To achieve an octet, the phosphorus atom forms an ion. the name of this ion is: phosphoride ion phosphic ion phosphorous ion phosphide

Phosphide ion

Explanation:

To achieve an octet, the phosphorus atom forms an ion. The name of this ion is Phosphide ion

Phosphorous have 15 electrons in shell. This means it has 5 electrons in its outer most shell well this means it requires 3 more electrons to complete its octate. Thus Phosphorus changes to phosphide ion with negative 3 sign  on it.