Explanation:
Atomic number is the total number of protons present in an element or atom. When an atom is neutral then it contains equal number of protons and electrons.
For example, there are 15 protons in a phosphorous atom that is, atomic number of phosphorous is 15.
Also, it is known that an atom has zero charge when it is neutral in nature.
Hence, we can conclude that the atomic number of phosphorus is 15. It has zero charge because it has same number of protons and electrons.