Isotopes of sodium

There are 21 recognized isotopes of sodium (11Na), ranging from 18
Na to 39
Na[2] and two isomers (22m
Na and 24m
Na). 23
Na is the only stable (and the only primordial) isotope. It is considered a monoisotopic element and it has a standard atomic weight of 22.98976928(2). Sodium has two radioactive cosmogenic isotopes (22
Na, half-life = 2.605 years; and 24
Na, half-life ≈ 15 hours). With the exception of those two, all other isotopes have half-lives under a minute, most under a second. The shortest-lived is 18
Na, with a half-life of 1.3(4)×10−21 seconds.

Main isotopes of sodium (11Na)
Iso­tope Decay
abun­dance half-life (t1/2) mode pro­duct
22Na trace 2.602 y β+ 22Ne
23Na 100% stable
24Na trace 14.96 h β− 24Mg
Standard atomic weight Ar, standard(Na)
  • 22.98976928(2)[1]

Acute neutron radiation exposure (e.g., from a nuclear criticality accident) converts some of the stable 23
Na in human blood plasma to 24
Na. By measuring the concentration of this isotope, the neutron radiation dosage to the victim can be computed.

22
Na is a positron-emitting isotope with a remarkably long half-life. It is used to create test-objects and point-sources for positron emission tomography.

List of isotopes
Nuclide[3]
[n 1]		 Z N Isotopic mass (Da)[4]
[n 2][n 3]		 Half-life
[n 4]		 Decay
mode
[n 5]		 Daughter
isotope
[n 6]		 Spin and
parity
[n 7][n 4]		 Natural abundance (mole fraction)
Excitation energy Normal proportion Range of variation
18Na 11 7 18.02688(10) 1.3(4)×10−21 s p 17Ne (1−)#
β+ (<.1%) 18Ne
19Na 11 8 19.013880(11) >10×10−18 s p 18Ne (5/2+)
20Na 11 9 20.0073544(12) 447.9(23) ms β+ (75%) 20Ne 2+
β+, α (25%) 16O
21Na 11 10 20.99765470(11) 22.422(10) s β+ 21Ne 3/2+
22Na 11 11 21.99443742(18) 2.6018(22) y β+ 22Ne 3+ Trace[n 8]
22m1Na 583.03(9) keV 243(2) ns IT 22Na 1+
22m2Na 657.00(14) keV 19.6(7) ps IT 22Na 0+
23Na 11 12 22.9897692820(19) Stable 3/2+ 1.0000
24Na 11 13 23.990963011(18) 14.957(4) h β− 24Mg 4+ Trace[n 8]
24mNa 472.207(9) keV 20.18(10) ms IT (99.95%) 24Na 1+
β− (.05%) 24Mg
25Na 11 14 24.9899540(13) 59.1(6) s β− 25Mg 5/2+
26Na 11 15 25.992635(4) 1.07128(25) s β− 26Mg 3+
26mNa 82.5(6) keV 9(2) µs IT 26Na 1+
27Na 11 16 26.994076(4) 301(6) ms β− (99.87%) 27Mg 5/2+
β−, n (0.13%) 26Mg
28Na 11 17 27.998939(11) 30.5(4) ms β− (99.42%) 28Mg 1+
β−, n (0.58%) 27Mg
29Na 11 18 29.002877(8) 44.1(9) ms β− (74.1%) 29Mg 3/2(+#)
β−, n (25.9%) 28Mg
30Na 11 19 30.009098(5) 48.4(17) ms β− (68.85%) 30Mg 2+
β−, n (30.0%) 29Mg
β−, 2n (1.15%) 28Mg
β−, α (5.5×10−5%) 26Ne
31Na 11 20 31.013147(15) 17.35(40) ms β− (61.78%) 31Mg (3/2+)
β−, n (37.3%) 30Mg
β−, 2n (0.87%) 29Mg
β−, 3n (0.05%) 28Mg
32Na 11 21 32.02001(4) 12.9(3) ms β− (68%) 32Mg (3−)
β−, n (24%) 31Mg
β−, 2n (8%) 30Mg
33Na 11 22 33.02553(48) 8.2(4) ms β−, n (47%) 32Mg (3/2+)
β− (40%) 33Mg
β−, 2n (13%) 31Mg
34Na 11 23 34.03401(64) 5.5(10) ms β−, 2n (50.0%) 32Mg 1+
β− (35.0%) 34Mg
β−, n (15.0%) 33Mg
35Na 11 24 35.04104(72)# 1.5(5) ms β− 35Mg 3/2+#
37Na 11 26 37.05747(74)# 1# ms [>1.5 µs] β−, n 36Mg 3/2+#
39Na[2] 11 28 β−, n (#) 38Mg
  1. mNa – 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. # – Values marked # are not purely derived from experimental data, but at least partly from trends of neighboring nuclides (TNN).
  5. Modes of decay:
    IT:Isomeric transition
    n:Neutron emission
    p:Proton emission
  6. Bold symbol as daughter – Daughter product is stable.
  7. ( ) spin value – Indicates spin with weak assignment arguments.
  8. Cosmogenic nuclide

Sodium-22

Sodium-22 is a radioactive isotope of sodium, undergoing positron emission to 22
Ne with a half-life of 2.605 years. 22
Na is being investigated as an efficient generator of "cold positrons" (antimatter) to produce muons for catalyzing fusion of deuterium. It is also commonly used as a positron source in positron annihilation spectroscopy.[5]

Sodium-24

Sodium-24 is one of the most important isotopes. It is radioactive and created from common sodium-23 by neutron bombardment. With a 15-hour half-life, 24
Na decays to 24
Mg by emission of an electron and two gamma rays. Exposure of the human body to intense neutron flux creates 24
Na in blood plasma. Measurements of its quantity are used to determine the absorbed radiation dose of the patient. This is used to determine the level of medical treatment required.

When the sodium-potassium alloy is used as a coolant in nuclear reactors, 24
Na is created, which makes the coolant radioactive. When the 24
Na decays, it causes a buildup of magnesium in the coolant. Since the half life is short, the 24
Na portion of the coolant ceases to be radioactive within a few days after removal from the reactor.

References
  1. Meija, Juris; et al. (2016). "Atomic weights of the elements 2013 (IUPAC Technical Report)". Pure and Applied Chemistry. 88 (3): 265–91. doi:10.1515/pac-2015-0305.
  2. Ahn, D.S.; et al. (2018). New isotope of 39Na and the neutron dripline of neon isotopes using a 345 MeV/nucleon 48Ca beam (PDF) (Report). RIKEN Accelerator Progress Reports. 51. p. 82.
  3. Half-life, decay mode, nuclear spin, and isotopic composition is sourced in:
    Audi, G.; Kondev, F. G.; Wang, M.; Huang, W. J.; Naimi, S. (2017). "The NUBASE2016 evaluation of nuclear properties" (PDF). Chinese Physics C. 41 (3): 030001. Bibcode:2017ChPhC..41c0001A. doi:10.1088/1674-1137/41/3/030001.
  4. Wang, M.; Audi, G.; Kondev, F. G.; Huang, W. J.; Naimi, S.; Xu, X. (2017). "The AME2016 atomic mass evaluation (II). Tables, graphs, and references" (PDF). Chinese Physics C. 41 (3): 030003-1–030003-442. doi:10.1088/1674-1137/41/3/030003.
  5. Saro, Matúš; Kršjak, Vladimír; Petriska, Martin; Slugeň, Vladimír (2019-07-29). "Sodium-22 source contribution determination in positron annihilation measurements using GEANT4". AIP Conference Proceedings. 2131 (1): 020039. doi:10.1063/1.5119492. ISSN 0094-243X.
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