Isotopes are the atoms of an element which have same atomic number but different mass number. So it is clear that they will have same number of electrons, same electronic configuration and thereby same number of valence electrons. Since in chemical reactions it is the valence electrons which participate, so we can conclude that isotopes have similar chemical properties.
They have different physical properties as they vary in their mass number and atomic mass. As atomic masses are different, therefore physical properties like boiling point, density etc will be different.