Isotopes of nitrogen

Natural nitrogen (₇N) consists of two stable isotopes: the vast majority (99.62%) of naturally occurring nitrogen is nitrogen-14, with the remainder (0.38%) being nitrogen-15. Thirteen radioisotopes are also known, with atomic masses ranging from 9 to 23, along with three nuclear isomers. All of these radioisotopes are short-lived, the longest-lived being ¹³N with a half-life of 9.965 minutes. All of the others have half-lives shorter than ten seconds. Isotopes lighter than the stable ones generally decay to isotopes of carbon, and those heavier beta decay to isotopes of oxygen.

Isotopes of nitrogen (₇N)

Main isotopes[1] Decay Isotope abun­dance half-life (t1/2) mode pro­duct 13N trace 9.965 min β+ 13C 14N 99.6% stable 15N 0.380% stable 16N synth 7.13 s β− 16O β−α<0.01% 12C
Standard atomic weight Ar°(N)
	[14.00643, 14.00728][2] 14.007±0.001 (abridged)[3]
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Nitrogen-13 is a positron emitter and one of the main isotopes used in medical PET scans.

List of isotopes

Nuclide [n 1]	Z	N	Isotopic mass (Da)[4] [n 2][n 3]	Half-life[1] [resonance width]	Decay mode[1] [n 4]	Daughter isotope [n 5]	Spin and parity[1] [n 6][n 7]	Natural abundance (mole fraction)
	Excitation energy							Normal proportion[1]	Range of variation
9 N[5]	7	2		<1 as[5]	5p[n 8]	4 He
10 N	7	3	10.04165(43)	143(36) ys	p ?	9 C ?	1−, 2−
11 N	7	4	11.026158(5)	585(7) ys [780.0(9.3) keV]	p	10 C	1/2+
11m N	740(60) keV			690(80) ys	p		1/2−
12 N	7	5	12.0186132(11)	11.000(16) ms	β+ (98.07(4)%)	12 C	1+
					β+α (1.93(4)%)	8 Be[n 9]
13 N[n 10]	7	6	13.00573861(29)	9.965(4) min	β+	13 C	1/2−
14 N[n 11]	7	7	14.003074004251(241)	Stable			1+	[0.99578, 0.99663][2]
14m N	2312.590(10) keV				IT	14 N	0+
15 N	7	8	15.000108898266(625)	Stable			1/2−	[0.00337, 0.00422][2]
16 N	7	9	16.0061019(25)	7.13(2) s	β− (99.99846(5)%)	16 O	2−
					β−α (0.00154(5)%)	12 C
16m N	120.42(12) keV			5.25(6) μs	IT (99.999611(25)%)	16 N	0−
					β− (0.000389(25)%)	16 O
17N	7	10	17.008449(16)	4.173(4) s	β−n (95.1(7)%)	16 O	1/2−
					β− (4.9(7)%)	17 O
					β−α (0.0025(4)%)	13 C
18 N	7	11	18.014078(20)	619.2(1.9) ms	β− (80.8(1.6)%)	18 O	1−
					β−α (12.2(6)%)	14 C
					β−n (7.0(1.5)%)	17 O
					β−2n ?	16 O ?
19 N	7	12	19.017022(18)	336(3) ms	β− (58.2(9)%)	19 O	1/2−
					β−n (41.8(9)%)	18 O
20 N	7	13	20.023370(80)	136(3) ms	β− (57.1(1.4)%)	20 O	(2−)
					β−n (42.9(1.4)%)	19 O
					β−2n ?	18 O ?
21 N	7	14	21.02709(14)	85(5) ms	β−n (87(3)%)	20 O	(1/2−)
					β− (13(3)%)	21 O
					β−2n ?	19 O ?
22 N	7	15	22.03410(22)	23(3) ms	β− (54.0(4.2)%)	22 O	0−#
					β−n (34(3)%)	21 O
					β−2n (12(3)%)	20 O
23 N[n 12]	7	16	23.03942(45)	13.9(1.4) ms	β− (> 46.6(7.2)%)	23 O	1/2−#
					β−n (42(6)%)	22 O
					β−2n (8(4)%)	21 O
					β−3n (< 3.4%)	20 O
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1. ^mN – Excited nuclear isomer.
2. ( ) – Uncertainty (1σ) is given in concise form in parentheses after the corresponding last digits.
3. # – Atomic mass marked #: value and uncertainty derived not from purely experimental data, but at least partly from trends from the Mass Surface (TMS).
4. Modes of decay:

   IT:	Isomeric transition
   n:	Neutron emission
   p:	Proton emission

5. Bold symbol as daughter – Daughter product is stable.
6. ( ) spin value – Indicates spin with weak assignment arguments.
7. # – Values marked # are not purely derived from experimental data, but at least partly from trends of neighboring nuclides (TNN).
8. Decays by proton emission to ⁸
   C, which immediately emits two protons to form ⁶
   Be, which in turn emits two protons to form stable ⁴
   He^[5]
9. Immediately decays into two alpha particles for a net reaction of ¹²N → 3 ⁴He + e⁺.
10. Used in positron emission tomography
11. One of the few stable odd-odd nuclei
12. Heaviest particle-bound isotope of nitrogen, see Nuclear drip line

Nitrogen-13

Main article: Nitrogen-13

Nitrogen-13 and oxygen-15 are produced in the atmosphere when gamma rays (for example from lightning) knock neutrons^[6] out of nitrogen-14 and oxygen-16:^[7]

¹⁴N + γ → ¹³N + n

¹⁶O + γ → ¹⁵O + n

¹³N decays to ¹³C, emitting a positron. The positron quickly annihilates with an electron, producing two gamma rays of about 511 keV. After a lightning bolt, this gamma radiation dies down with a half-life of 10 minutes, but these low-energy gamma rays go on average only about 90 metres through the air, so they may only be detected for a minute or so as the "cloud" of ¹³N and ¹⁵O floats by, carried by the wind.^[8]

Nitrogen-14

Nitrogen-14 makes up the clear majority of natural nitrogen, about 99.62%, and is responsible for the Earth's stable atmosphere.

Nitrogen-14 is one of the very few stable nuclides with both an odd number of protons and of neutrons (seven each) and is the only one to make up a majority of its element. Unpaired protons or neutrons contribute a half-integer nuclear spin, which in this case is a spin 1/2 orbital, giving the nucleus a total magnetic spin of one (as the spins prefer to align).

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 CNO 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 5700 years.

Nitrogen-15

Nitrogen-15 is a rare stable isotope of nitrogen, comprising about 0.38%. Nitrogen-15 presents one of the lowest thermal neutron capture cross sections of all isotopes.^[9]

Nitrogen-15 is frequently used in NMR (Nitrogen-15 NMR spectroscopy). Unlike the more abundant nitrogen-14, which has an integer nuclear spin and thus a quadrupole moment, ¹⁵N has a fractional nuclear spin of one-half, which offers advantages for NMR such as narrower line width. As most nitrogen NMR studies look at a single nitrogen atom in an organic molecule, isotopic labeling is feasible.

Nitrogen-15 tracing is a technique used to study the nitrogen cycle.

Nitrogen-16

The radioisotope ¹⁶N is the dominant radioactivity source in the coolant water of nuclear reactors cooled by water during normal operation. It is produced from ¹⁶O (in water) via an (n,p) reaction, in which the ¹⁶O atom captures a neutron and expels a proton. It has a short half-life of 7.13 seconds, but its decay back to ¹⁶O produces high-energy gamma radiation (6.13 MeV principal line^[10]).^[11] Because of this, access to the primary coolant piping in a pressurised water reactor must be restricted during reactor power operation.^[11] It is a sensitive and immediate indicator of leaks from the primary coolant system to the secondary steam cycle and is the primary means of detection for such leaks.^[11]

Isotopic signatures

Main article: Isotopic signature § Nitrogen isotopes

See also

Daughter products other than nitrogen

• Isotopes of oxygen
• Isotopes of carbon
• Isotopes of beryllium
• Isotopes of helium