Sodium-24

Main isotopes of sodium

Isotope			Decay
	abundance	half-life	mode	energy (MeV)	product
²²Na	trace	2.602 y	β⁺→γ	0.5454	²²Ne*
			β⁺→γ	1.27453(2)	²²Ne
			ε→γ	–	²²Ne*
			ε→γ	1.27453(2)	²²Ne
			β⁺	1.8200	²²Ne
²³Na	100%	is stable with 12 neutrons
²⁴Na	trace	14.96 h	β⁻	5.5155	²⁴Mg

Standard atomic weight (A_r)

7001229897692800000♠22.98976928(2)

There are twenty recognized isotopes of sodium (₁₁Na), 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 standard atomic weight of 7001229897692800000♠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.

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.

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