An isotope of Nitrogen has an atomic number of 7 and a mass number of 15. How many electrons, neutrons, and protons does an atom of this isotope have?

Atomic number = the number of protons per atom of this isotopeMass number = total number of protons + neutrons per atom
Therefore, an atom of this isotope has 7 protons and 15-7=8 neutrons.
As an atom is neutral, the number of electrons = number of protons. Therefore, an atom of this isotope has 7 electrons.