Chlorine atoms each have 17 protons. how many neutrons does each cl-37 atom have? a. 17 b. 20 c. 37 d. 54

The chlorine-37 has 20 neutrons.

Explanations:

1) When an atom of chlorine-35, then it  contains 18 neutrons.

                                    mass =  17 protons + 18 neutrons = 35

2) When an atom of chlorine-37 then it contains 20 neutrons

                                   mass = 17 protons + 20 neutrons = 37

Note: Adding or removing a neutron from an atom's nucleus creates isotopes of a particular element