How many protons, electrons and neutrons does a phosphorus atom have?

From a periodic table, we can see that the atomic number of phosphorus (the smaller number) is 15, so that means that phosphorus has 15 protons. An atom does not have a charge, and so number of protons=number of electrons. Phosphorus also has 15 electrons. A periodic table also gives us the mass number of phosphorus (the bigger number) which is 31. This number is equal to protons + neutrons in an atom, so mass number - protons = neutrons. 31 - 15 = 16, so phosphorus has 16 neutrons.