What does the superscript of an isotope notation mean?
This represents the NUMBER of nuclear particles....
Let's take a simple example, i.e. for hydrogen, the MOST abundant element in this universe. Most hydrogen nuclei contain the ONE nuclear particle, i.e. one proton....and we would represent this ISOTOPE as
A smaller percentage of hydrogen atom necessarily contain the DEFINING proton, and ALSO a neutron...to give the
And an even smaller percentage of hydrogen atoms, contain the
And so the superscripted number is the number of