In nature, chlorine exists in two isotopic forms, with masses 35 u and 37 u in the ratio of _________________.

In nature, chlorine exists in two isotopic forms with masses of 35 u and 37 u in a 3:1 ratio.

Chlorine has two isotopes having atomic masses of $35u$ and $37u$ each, present in the ratio 3:1.The average atomic mass of the Chlorine atom will be, Average atomic mass $=$ (Mass of isotope $\times$ Relative abundance )