Isotopes of nitrogen

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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 relative atomic mass of nitrogen is 14.0067.

Natural isotopes[edit]

Nitrogen-14[edit]

Nitrogen-14 is one of two stable (non-radioactive) isotopes of the chemical element nitrogen, which makes 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, radioactive, carbon-14. Some kinds of cosmic radiation cause a nuclear reaction with nitrogen-14 in the upper atmosphere of the Earth, creating carbon-14, which decays back to nitrogen-14 with a half-life of 5,730±40 years.[1]

Nitrogen-15[edit]

Nitrogen-15, or 15N, is a rare stable isotope of nitrogen. Two sources of nitrogen-15 are the positron emission of oxygen-15[2] and the beta decay of carbon-15. Nitrogen-15 presents one of the lowest thermal neutron capture cross sections of all isotopes.[3]

Nitrogen-15 is frequently used in NMR (Nitrogen-15 NMR spectroscopy). Unlike the more abundant nitrogen-14, that has an integer nuclear spin and thus a quadrupole moment, 15N has a fractional nuclear spin of one-half, which offers advantages for NMR like narrower line width.

Isotopic signatures[edit]

Table[edit]

nuclide
symbol
Z(p) N(n)  
isotopic mass (u)
 
half-life decay mode(s)[4] 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 9C (2−)
11N 7 4 11.02609(5) 590(210)×10−24 s
[1.58(+75−52) MeV]
p 10C 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%) 12C 1+
β+, α (3.5%) 8Be[n 2]
13N[n 3] 7 6 13.00573861(29) 9.965(4) min β+ 13C 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%) 16O 2−
β, α (.001%) 12C
17N 7 10 17.008450(16) 4.173(4) s β, n (95.0%) 16O 1/2−
β (4.99%) 17O
β, α (.0025%) 13C
18N 7 11 18.014079(20) 622(9) ms β (76.9%) 18O 1−
β, α (12.2%) 14C
β, n (10.9%) 17O
19N 7 12 19.017029(18) 271(8) ms β, n (54.6%) 18O (1/2−)
β (45.4%) 19O
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−#
  1. ^ Bold for stable isotopes
  2. ^ Immediately decays into two alpha particles for a net reaction of 12N -> 34He + e+
  3. ^ Used in positron emission tomography

Notes[edit]

  • The precision of the isotope abundances and atomic mass is limited through variations. The given ranges should be applicable to any normal terrestrial material.
  • Values marked # are not purely derived from experimental data, but at least partly from systematic trends. Spins with weak assignment arguments are enclosed in parentheses.
  • Uncertainties are given in concise form in parentheses after the corresponding last digits. Uncertainty values denote one standard deviation, except isotopic composition and standard atomic mass from IUPAC, which use expanded uncertainties.
  • Nuclide masses are given by IUPAP Commission on Symbols, Units, Nomenclature, Atomic Masses and Fundamental Constants (SUNAMCO).
  • Isotope abundances are given by IUPAC Commission on Isotopic Abundances and Atomic Weights.

References[edit]

  1. ^ Godwin, H (1962). "Half-life of radiocarbon". Nature. 195 (4845): 984. Bibcode:1962Natur.195..984G. doi:10.1038/195984a0. 
  2. ^ CRC Handbook of Chemistry and Physics (64th ed.). 1983–1984. p. B-234. 
  3. ^ "Evaluated Nuclear Data File (ENDF) Retrieval & Plotting". National Nuclear Data Center. 
  4. ^ "Universal Nuclide Chart". nucleonica. (registration required (help)). 


Isotopes of carbon Isotopes of nitrogen Isotopes of oxygen
Table of nuclides