Atomic number of phosphorus is 15.the number of electronic confugirationĀ are 2,8,5.when the atom gains 3 electron the orbit is filled.or other wise the atoms should loose 5 electrons.the valency is the combining capacity of the atom.therefore the valeny of phosphorus is 3 and 5
Phosphorus(Atomic no. 15) has its electrons arranged in a configuration of 2,8,5. Now, orbits are stable when they are full. InĀ this case, The outer orbit must have eight electrons for stability in combining with other elements, also known as valency. So one can either add 3 electrons to the outer orbit or take away 5 electrons with equal ease. So Phosphorus has a valency of 3 or 5.