Answer:
17 protons and 20 neutrons
Step-by-step explanation:
Chlorine (Cl) is an element of the periodic table whose atomic number is 17 and enters the group of halogens.
Cl37 is a stable isotope (atom from an element with the same atomic number but different atomic mass) of chlorine.
Is an isotope of chlorine found in nature, representing ~24% of the total.