How can elements have different isotopes?

Hint: The word isotope is generally made up from two Greek words called isos and topes which have the meaning “the same place”. The reason for using this word is to identify that isotopes variants of a single element are found in the same position of the periodic table.

Complete answer:
The term isotope was first used by Scottish doctor Margaret Todd. Isotope mainly refers to the variation in the atomic mass or atomic weight of an element or we can also say those elements which have the same number of protons but different numbers of neutrons.
The isotopes of an element generally show different masses; this is due to the unequal numbers of neutrons present in them. Generally the elements which have odd atomic numbers will have one or two stable isotopes whereas elements with even atomic numbers will mostly have 3 or more stable isotopes. However exceptions are also there in carbon, helium and beryllium atoms.
An isotope is generally represented by the name of the particular element at the beginning which is followed by a hyphen and the mass number. Isotopes are said to be either stable or radioactive and the isotopes which are radioactive are known by the name radioisotopes or radionuclides.

Note:
Different isotopes have nearly identical chemical behaviors but different physical properties like mass, melting or boiling point, density, and the freezing point because the physical properties of any isotope mostly depend on the mass of each isotope.