Natural Nitrogen (N) consists of two stable isotopes, nitrogen-14, which makes up the vast majority of naturally occurring nitrogen, and nitrogen-15. Fourteen radioactive isotopes (radioisotopes) have also been found so far, with atomic masses ranging from 10 to 25, and one nuclear isomer, 11mN. All of these radioisotopes are short-lived, with the longest-lived one being nitrogen-13 with a half-life of 9.965 minutes. All of the others have half-lives below 7.15 seconds, with most of these being below five-eighths of a second. Most of the isotopes with atomic mass numbers below 14 decay to isotopes of carbon, while most of the isotopes with masses above 15 decay to isotopes of oxygen. The shortest-lived known isotope is nitrogen-10, with a half-life of about 2.3 microseconds.
The standard atomic mass of nitrogen is 14.0067 atomic mass units.
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Nitrogen-14 is one of two stable (non-radioactive) isotopes of the chemical element nitrogen, which makes up about 99.636% of natural nitrogen.
Nitrogen-14 is one of the very few stable nuclides with both an odd number of protons and of neutrons (seven each). Each of these contributes a nuclear spin of plus or minus spin 1/2, giving the nucleus a total magnetic spin of one.
Like all elements heavier than lithium, the original source of nitrogen-14 and nitrogen-15 in the Universe is believed to be stellar nucleosynthesis, where they are produced as part of the carbon-nitrogen-oxygen cycle.
Nitrogen-14 is the source of naturally-occurring carbon-14. Some kinds of cosmic radiation causes a nuclear reaction with nitrogen-14 in the upper atmosphere of the Earth, creating the carbon-14. This radioisotope decays back to nitrogen-14 after a half-life of several thousand years.
Nitrogen-15 is a rare stable isotope of nitrogen. This isotope is often used in agricultural and medical research, for example in the Meselson–Stahl experiment to establish the nature of DNA replication.[1] An extension of this research resulted in development of DNA-based stable-isotope probing, which allows examination of links between metabolic function and taxonomic identity of microorganisms in the environment, without the need for culture isolation.[2][3] Nitrogen-15 is extensively used to trace mineral nitrogen compounds (particularly fertilizers) in the environment and when combined with the use of other isotopic labels, is also a very important tracer for describing the fate of nitrogenous organic pollutants.[4][5]
Nitrogen-15 is frequently used in nuclear magnetic resonance spectroscopy (NMR), because unlike the more abundant splinless nitrogen-14, it has a fractional nuclear spin of one-half, which makes it observable by NMR. Proteins can be isotopically labelled by cultivating them in a medium containing nitrogen-15 as the only source of nitrogen. In addition, nitrogen-15 is used to label proteins in quantitative proteomics (e.g. SILAC).
Two sources of nitrogen-15 is by the positron emission of oxygen-15[6] and the beta decay of carbon-15.
| nuclide symbol |
Z(p) | N(n) | isotopic mass (u) |
half-life | decay mode(s)[7] | daughter isotope(s)[n 1] |
nuclear spin |
representative isotopic composition (mole fraction) |
range of natural variation (mole fraction) |
|---|---|---|---|---|---|---|---|---|---|
| excitation energy | |||||||||
| 10N | 7 | 3 | 10.04165(43) | 200(140)×10−24 s [2.3(16) MeV] |
p | 9 C |
(2−) | ||
| 11N | 7 | 4 | 11.02609(5) | 590(210)×10−24 s [1.58(+75−52) MeV] |
p | 10 C |
1/2+ | ||
| 11mN | 740(60) keV | 6.90(80)×10−22 s | 1/2− | ||||||
| 12N | 7 | 5 | 12.0186132(11) | 11.000(16) ms | β+ (96.5%) | 12 C |
1+ | ||
| β+, α (3.5%) | 8 Be[n 2] |
||||||||
| 13N[n 3] | 7 | 6 | 13.00573861(29) | 9.965(4) min | β+ | 13 C |
1/2− | ||
| 14N | 7 | 7 | 14.0030740048(6) | Stable | 1+ | 0.99636(20) | 0.99579–0.99654 | ||
| 15N | 7 | 8 | 15.0001088982(7) | Stable | 1/2− | 0.00364(20) | 0.00346–0.00421 | ||
| 16N | 7 | 9 | 16.0061017(28) | 7.13(2) s | β− (99.99%) | 16 O |
2− | ||
| β−, α (.001%) | 12 C |
||||||||
| 17N | 7 | 10 | 17.008450(16) | 4.173(4) s | β−, n (95.0%) | 16 O |
1/2− | ||
| β− (4.99%) | 17 O |
||||||||
| β−, α (.0025%) | 13 C |
||||||||
| 18N | 7 | 11 | 18.014079(20) | 622(9) ms | β− (76.9%) | 18 O |
1− | ||
| β−, α (12.2%) | 14 C |
||||||||
| β−, n (10.9%) | 17 O |
||||||||
| 19N | 7 | 12 | 19.017029(18) | 271(8) ms | β−, n (54.6%) | 18 O |
(1/2−) | ||
| β− (45.4%) | 19 O |
||||||||
| 20N | 7 | 13 | 20.02337(6) | 130(7) ms | β−, n (56.99%) | 19O | |||
| β− (43.00%) | 20O | ||||||||
| 21N | 7 | 14 | 21.02711(10) | 87(6) ms | β−, n (80.0%) | 20O | 1/2−# | ||
| β− (20.0%) | 21O | ||||||||
| 22N | 7 | 15 | 22.03439(21) | 13.9(14) ms | β− (65.0%) | 22O | |||
| β−, n (35.0%) | 21O | ||||||||
| 23N | 7 | 16 | 23.04122(32)# | 14.5(24) ms [14.1(+12−15) ms] |
β− | 23O | 1/2−# | ||
| 24N | 7 | 17 | 24.05104(43)# | <52 ns | n | 23N | |||
| 25N | 7 | 18 | 25.06066(54)# | <260 ns | 1/2−# | ||||
| Isotopes of carbon | Isotopes of nitrogen | Isotopes of oxygen |
| Index to isotope pages · Table of nuclides | ||