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Isotopes of sodium

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There are twenty recognized isotopes of sodium, ranging from 18
Na
to 37
Na
and two isomers (22m
Na
and 24m
Na
). 23
Na
is the only stable (and the only primordial) isotope. As such, it is considered a monoisotopic element and it has a relative atomic mass: 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 6979129999999999999♠1.3(4)×10−21 seconds.

Contents

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.

Notes

  • 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.
  • 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.

    Sodium-22

    Sodium-22 is being investigated as an efficient generator of “cold positrons” (essentially antimatter) to produce muons for catalyzing fusion of deuterium. The energy released would induce phenomenal specific impulse in a rocket engine, enabling probe missions to reach any outer planet in a few weeks instead of years or Alpha Centauri in less than a decade.

    References

    Isotopes of sodium Wikipedia