Final answer:
An atom of 197Au has 79 protons, 118 neutrons, and 79 electrons, with the number of neutrons calculated by subtracting the atomic number from the mass number.
Step-by-step explanation:
The atom of gold referred to by the symbol 197Au (A = 197, Z = 79) has 79 protons, which is the atomic number of gold (Z). The mass number of this isotope (A) is 197. The number of neutrons is found by subtracting the atomic number from the mass number, which is 197 - 79 = 118 neutrons. An atom of gold in its neutral state has an equal number of electrons as protons, so it also has 79 electrons. In summary, 197Au has 79 protons, 118 neutrons, and 79 electrons.