atomic number from mass number. mass number from atomic number. atomic number from electron number. isotope number from electron number.
I gave my students this multiple choice question: The number of neutrons in an atom is found by subtracting

Only one answer is correct among these 4 choices:
- atomic number from mass number.
- mass number from atomic number.
- atomic number from electron number.
- isotope number from electron number.

Could you tell me which one is correct?

atomic number from mass number.