Question

What do isotopes of an element have in common? How do they differ?

Answer 1

It is the electrons that determine the chemical behaviour of a particular element. Isotopes of an element share the same number of protons but have different numbers of neutrons

Answer 2

Isotopes are atoms of the same element that have different numbers of neutrons but the same number of protons and electrons. The difference in the number of neutrons between the various isotopes of an element means that the various isotopes have different masses.