An Isotope is the atoms of an element with different numbers of neutrons that have the same proton number, but different mass numbers. A different mass size is due to the difference in the number of neutrons that an atom contains.
An Isotope is the atoms of an element with different numbers of neutrons that have the same proton number, but different mass numbers. A different mass size is due to the difference in the number of neutrons that an atom contains.