nitrogen14

Nitrogen-14 (14N) is a stable isotope of the element nitrogen, defined by having 7 protons and 7 neutrons and a mass number of 14. It is the most abundant nitrogen isotope, making up about 99.6% of natural nitrogen, while nitrogen-15 (15N) accounts for the remaining ~0.4%.

The 14N nucleus has a nuclear spin of I = 1 and a nonzero quadrupole moment. This quadrupole nature leads to broad signals and limited visibility in high-resolution NMR, which is one reason 15N is often used for nitrogen-labeling studies in biochemistry and structural biology.

In nature, 14N is found predominantly in the diatomic molecule N2, which constitutes the majority of Earth's atmospheric nitrogen. The isotope is stable and non-radioactive, so it does not decay over time. The natural abundance ratio of 14N to 15N is about 270:1, though this ratio varies slightly due to geological and biological processes and is routinely exploited in isotopic tracing and environmental studies.

Historically, the existence of nitrogen isotopes was demonstrated in the early 20th century through mass spectrometry, which revealed multiple stable isotopes for nitrogen. The predominance of 14N means it provides the baseline for many isotopic measurements, with 15N-enriched compounds used to track nitrogen through biological systems and to study nitrogen cycling in ecology and earth science.

Applications of nitrogen-14 include serving as the reference isotope in isotopic analyses, baseline measurements for environmental and forensic studies, and informing general understanding of nitrogen's role in chemistry and biology.