Isotopes of an element have ________ chemical properties, because they have same number of _______ in their nucleus.

Isotopes: Atoms of an element having the same number of protons and electrons but different numbers of neutrons.

Reason for the same chemical properties:

• A chemical property is determined by the ability of a substance to undergo a chemical change.
• A chemical change occurs during a chemical reaction.
• During a chemical reaction, there is the involvement of electrons. So it is safe to say that chemical properties are determined by the electrons and their electronic configuration.
• Isotopes of Chlorine (Cl) i.e.; ${}_{17}{}^{35}\mathrm{Cl}$ and ${}_{17}{}^{37}\mathrm{Cl}$ have same number of electrons i.e.; 17 and their electronic configuration is 2, 8, 7.
• In an atom that is a neutral species, number of electrons is equal to the number of protons in the nucleus and they have the same chemical properties.

Therefore, isotopes of an element have the same chemical properties, because they have same number of protons in their nucleus.