Protons = 7Neutrons = 8Electrons = 7This N-15 isotope has an atomic number of 7 - this is equivalent to the number of protons.The atom is not charged and so will have the same number of electrons as protonsThe mass number is equivalent to the number of protons + the number of neutrons (mass of electrons is negligible). We have 7 protons so the number of neutrons must be 15 -7 which equals 8.