Nitrogen-15 is a stable isotope of nitrogen, which means it has a specific number of neutrons in its nucleus. It contains seven protons and eight neutrons, giving it a mass number of 15. This isotope occurs naturally, making up about 0.36% of all nitrogen found in the environment. Nitrogen-15 is often used in scientific research, particularly in agriculture and environmental studies. Researchers utilize it to trace nitrogen cycles and understand how plants absorb nutrients. Its unique properties help scientists study ecological interactions and the effects of fertilizers on soil health.