Question

why does chlorine 35 and chlorine 37 have same chemical properties in which respect does these atom differ

Answer 1

thes are the Isotopes of the chlorine

Answer 2

Cl-35 and Cl-37 are isotopes i.e. they have same no. of electrons but different no. of neutrons.
Since chemical properties depends on electrons therefore isotopes have same chemical properties.
Isotopes differ by their mass number or rather the no. of neutrons present in their nucleus.