Nitrogen-14's a stable, non-radioactive isotope of the chemical element nitrogen. Nitrogen-14 comprises approximately 99% of all naturally formed nitrogen. It's the source of naturally-occurring carbon-14, which's created when cosmic radiation interacts with nitrogen-14 in the upper atmosphere. It's also formed from the radioactive decay of carbon-14. However, like all elements heavier than helium, the original source of nitrogen-14 in the universe's believed to be stellar nucleosynthesis. It'… (More on Nitrogen-14)