Question

What is the charge of the nucleus of a phosphorus atom, and how do you know?

Answer 1

As we know charge on nucleus is positive so no matter which is the atom the charge will be positive.

Answer 2

hydrogen has 1 proton, so that's its atomic number. 15 is the atomic number, so you know phosphorus has 15 protons. Since protons are equal to electrons, there are 15 electrons. The mass is 31.0, which is the # of protons and # neutrons added together.