Question

why do 35\17 Cl and 37\17Clhave the same chemical properties in what respect do this atoms differ

Answer 1

They have same atomic number but different mass number. Ss they have same atomic number, they have similar chemical properties. They are called as Isotopes.

Answer 2

atomic no. is responsible for the chemical properties of an element. since the atomic no. of both these species is same these have same chemical properties and differ in chemical properties.
the atoms differ in physical properties.