Cl³⁵ and Cl³⁷ will have same valencies. These are two isotopes of Chlorine. The atoms of same elements which have the same atomic numbers but different mass numbers are known as isotopes. Isotopes have same chemical properties but different physical properties. Both Cl³⁵ and Cl³⁷ have same atomic number, hence the number of electron in both of these atoms will be same. This will result in similar valencies.