Definition - What does Isotopes mean?
Isotopes are different versions of an element that have the same atomic number (number of protons in the atom), but have different amounts of neutrons. This means that they behave in the same way chemically and remain the same element no matter how many neutrons they have, but the protons remain the same. There are as many isotopes as there are different possible numbers of neutrons an element can have.
Safeopedia explains Isotopes
When an atom becomes an isotope and the amount of neutrons it has changes, it will behave in exactly the same manner and look exactly the same, as well as keep it's place and name in the periodic table, so long as its number of protons remains the same. However, its atomic mass changes and it can become unstable and radioactively decay.