What are all the possible masses of cl2 molecules that are made when two chlorine atoms bond together?

The masses of the 2 most common isotopes of Cl are 35 and 37. Therefore we can formulate 3 possible masses of Cl2:

35 + 35 = 70

35 + 37 = 72

37 + 37 = 74

However, Cl 35 is the most common isotope of chlorine of the two therefore it is the most probable that two Cl 35 atoms will combine, so 70 is the most common among all.