Isotopes of sodium

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 (05 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 least stable is ¹⁸
Na, with a half-life of 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.

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.

Table

nuclide symbol	Z(p)	N(n)	isotopic mass (u)	half-life	decay mode(s)	daughter isotope(s)	nuclear spin	representative isotopic composition (mole fraction)	range of natural variation (mole fraction)
	excitation energy
18Na	11	7	18.02597(5)	1.3(4)×10−21 s	p (>99.9%)	17Ne	(1−)#
					β+ (<.1%)	18Ne
19Na	11	8	19.013877(13)	<40 ns	p	18Ne	(5/2+)#
20Na	11	9	20.007351(7)	447.9(23) ms	β+ (75%)	20Ne	2+
					β+, α (25%)	16O
21Na	11	10	20.9976552(8)	22.49(4) s	β+	21Ne	3/2+
22Na	11	11	21.9944364(4)	2.6027(10) y	β+	22Ne	3+	Trace
22mNa	583.03(9) keV			244(6) ns			1+
23Na	11	12	22.9897692809(29)	Stable			3/2+	1.0000
24Na	11	13	23.99096278(8)	14.9590(12) h	β−	24Mg	4+	Trace
24mNa	472.207(9) keV			20.20(7) 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	25.992633(6)	1.077(5) s	β−	26Mg	3+
27Na	11	16	26.994077(4)	301(6) ms	β− (99.87%)	27Mg	5/2+
					β−, n (.13%)	26Mg
28Na	11	17	27.998938(14)	30.5(4) ms	β− (99.421%)	28Mg	1+
					β−, n (.579%)	27Mg
29Na	11	18	29.002861(14)	44.9(12) ms	β− (74.09%)	29Mg	3/2(+#)
					β−, n (25.91%)	28Mg
30Na	11	19	30.008976(27)	48.4(17) ms	β− (68.83%)	30Mg	2+
					β−, n (30.0%)	29Mg
					β−, 2n (1.17%)	28Mg
					β−, α	26Ne
31Na	11	20	31.01359(23)	17.0(4) ms	β− (62.05%)	31Mg	(3/2+)
					β−, n	30Mg
					β−, 2n	29Mg
					β−, 3n	28Mg
32Na	11	21	32.02047(38)	12.9(7) ms	β−	32Mg	(3−,4−)
					β−, n	31Mg
					β−, 2n	30Mg
33Na	11	22	33.02672(94)	8.2(2) ms	β−, n (52.0%)	32Mg	3/2+#
					β− (36.0%)	33Mg
					β−, 2n (12.0%)	31Mg
34Na	11	23	34.03517(96)#	5.5(10) ms	β−, 2n (50.0%)	32Mg	1+
					β− (35.0%)	34Mg
					β−, n (15.0%)	33Mg
35Na	11	24	35.04249(102)#	1.5(5) ms	β− (>99.9%)	35Mg	3/2+#
					β−, n (<.1%)	34Mg
36Na	11	25	36.05148(102)#	<260 ns
37Na	11	26	37.05934(103)#	1# ms [>1.5 µs]			3/2+#

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.

Lighter: sodium-23	Isotopes of sodium is an isotope of sodium	Heavier: sodium-25
Decay product of: neon-24	Decay chain of isotopes of sodium	Decays to: magnesium-24

References

• Isotope masses from:
• Isotopic compositions and standard atomic masses from:
• Half-life, spin, and isomer data selected from the following sources. See editing notes on this article's talk page.

External links

• Sodium isotopes data from The Berkeley Laboratory Isotopes Project's

Isotopes of neon	Isotopes of sodium	Isotopes of magnesium
Table of nuclides