Question

Why do ${\displaystyle {}_{17}^{35}\text{CI}}$ and ${\displaystyle {}_{17}^{37}\text{CI}}$  have the same chemical properties? In what respect do these atoms differ?

Answer 1

Only electrons take part in chemical reactions. Chemical properties depend on the electronic configuration. Isotopes of the element Cl ${\displaystyle {}_{17}^{35}\text{CI}}$ and ${\displaystyle {}_{17}^{37}\text{CI}}$ have the same atomic number, and hence, the same configuration. So, they have the same chemical properties. These differ only in physical contents and weights because neutrons contribute to the mass of an atom. ${\displaystyle {}_{17}^{35}\text{CI}}$ and ${\displaystyle {}_{17}^{37}\text{CI}}$ have different number of neutrons 18 and 20, respectively.