Nickel is the transitional metal in the compound
The overall charge of the compound Ni₃P
= the sum of the charges of element × the number number of atoms
Because Ni₃P is a neutral compound, then the overall charge of the compound is zero.
⇒ 3 (charge of Ni) + (charge of P) = 0
⇒ 3 (charge of Ni) = - (charge of P) [Redox Rules: Group 15
elements of -3.]
⇒ 3 (charge of Ni) = - (-3)
(charge of Ni) = + 1