Final answer:
The nucleus of the element phosphorus (P) contains 15 protons, as indicated by its atomic number, which is 15. This is consistent across all isotopes of phosphorus.
Step-by-step explanation:
In answering the question of how many protons are present in the nucleus of the element with the symbol P, we can look at periodic table information or use given data. The atomic number, which is a unique identifier for an element, directly tells us the number of protons in an atom of that element. In this case, the element phosphorus (P) has an atomic number of 15, which means that the nucleus of a phosphorus atom contains 15 protons. It's also noted that isotopes of an element have the same number of protons but different numbers of neutrons. For example, the isotope mentioned with 15 neutrons and 15 protons still has 15 protons in its nucleus.