Home ยป An atom has a mass number of 37 and atomic number 17. How many protons does it have? Atomic Structure MCQs An atom has a mass number of 37 and atomic number 17. How many protons does it have? January 8, 2022 10 Views Q. An atom has a mass number of 37 and atomic number 17. How many protons does it have? A. 20 B. 54 C. 17 D. 21 Answer: 17