Phosphorous can form an ion called phosphide, which has the formula p3−.
this ion

a. contains 18 electrons
b. forms when a phosphorus atom loses three protons
c. has properties very similar of p
d. is called a cation

A. contains 18 electrons

Explanation:

Atomic number is defined as the number of protons or number of electrons that are present in an atom. It is characteristic of an element.

Atomic number of phosphorous is 15.

The electronic configuration of phosphorous (P) will be,

Atomic number = Number of electrons = Number of protons = 15

As the phosphorous atom has gained 3 electrons, it will have 15+3= 18 electrons , the phosphorous anion will be having a charge of -3.

The electronic configuration of will be,

Thus the correct statement is this ion contains 18 electrons