Stable Isotopes

Intro
 

What is a stable isotope?
A stable isotope is any of two or more forms of an element whose nuclei contains the same number of protons,
but a different number of neutrons. Stable isotopes remain unchanged indefinitely, but unstable (radioactive) isotopes
undergo spontaneous disintegration. An isotopically labeled compound has one or more of its atoms enriched in
an isotope.