How many valence electrons are in an atom of phosphorus?

5
configuration is:
##1s^2 2s^2 2p^6 3s^2 3p^3##
The are found in the highest energy level (row) of in the s and p orbitals. ##3s^2 3p^3##
The pnictogens or nitrogen group is a significant element family.
They are also called Group 15 or VA or the Nitrogen Group.
All have 5 valence electrons with diverse properties, intermediate between those of metals and nonmetals and the best known member of this group is nitrogen. Phosphorus is also a member.