Sodium-24

Properties and data of the isotope ²⁴Na.

Contents

General Data

Radioactive Decay

Parent Nuclides

Isotones und Isobares

Literature

Sodium-24 is a radioisotope of the chemical element sodium, which, in addition to the element-specific 11 protons, has 13 neutrons in the atomic nucleus, resulting in the mass number 13.

As a cosmogenic nuclide, ²⁴Na is formed by the action of cosmic radiation in the atmosphere from the naturally occurring argon-40, but - due to the short half-life of just under 15 hours - can only be detected in small quantities. The natural decay product is the stable magnesium-24.

The nuclide ²⁴Na can be produced synthetically by irradiating of conventional sodium, which consists of 100% of the stable isotope sodium-23, with neutrons:

²³Na(n, γ)²⁴Na.

However, there are no practical technical applications for the isotope.

The same reaction to form sodium-24 becomes more important wherever neutrons emerge and hit sodium. This is the case, for example, in certain nuclear reactors that are cooled with Na, but also in nuclear accidents and after the use of nuclear weapons: sodium used as a coolant, such as in the French Superphénix fast breeder reactor in Creys-Malville, changes in the reactor room partly in Na-24 and therefore becomes radioactive.

The acute exposure of the human body to neutrons also produces the radioactive nuclide from the Na salts contained in tissue and body fluids. In a recent research paper [3], a dosimetry technique is proposed with which the radioactivity induced by neutron exposure in body tissue can be measured and assessed by measuring ²⁴Na activity in hair and blood samples using gamma-ray spectrometry.

The discovery of the radioactive isotope during the irradiation of magnesium-24 with neutrons was reported in 1934 [1]:

²⁴Mg(n,p)²⁴Na.

See also: List of individual Sodium isotopes (and general data sources).

General data

Name of the isotope:Sodium-24; Na-24Symbol:²⁴Na or 2411NaMass number A:24 (= number of nucleons)Atomic number Z:11 (= number of protons)Neutrons N:13Nucleon pairing (Z - N):odd - oddNuclear ratio (N/Z ratio):1.1818181818182 (= neutron-proton ratio)Neutron excess (N-Z):2Isotopic mass:23.990963012(18) u (atomic weight of Sodium-24)Nuclide mass:23.9849287 u (calculated nuclear mass without electrons)Mass excess:-8.4179 MeVMass defect:0.207756248 u (per nucleus)Nuclear binding energy:193.52369847 MeV (per nucleus)
8.06348744 MeV (average binding energy per nucleon)Separation energy:S_N = 6.959365(17) MeV (first neutron)
S_P = 10.55283(11) MeV (first proton)Half-life:14.956(3) hDecay constant λ:1.287372646929 × 10^-5 s^-1Specific activity α:3.370756269148 × 10⁺¹⁷ Bq g^-1
9110152.0787789 Ci g^-1Spin and parity:
(nuclear angular momentum)4+Magnetic dipole moment:μ(μ_N) = +1.6903(8)Nuclear g-factor:g_l = 0.422575Charge radius:2.9735(168) femtometer fmMirror nucleus:Aluminium-24Year of discovery:1934

Radioactive Decay

Half-life T_½ = 14.956(3) h (hours) respectively 5.3842 × 10⁴ seconds s.

Decay mode	Daughter	Probability	Decay energy	γ energy (intensity)
β^-	²⁴Mg	100 %	5.515677(21) MeV	1368.625(5) keV 99.94(2) % 2754.008(11) keV (99.867(10) %)

The figure shows the formation and radioactive decay of the radionuclide ²⁴Na.

Parent Nuclides

Direct parent isotope is: ²⁴Ne.

Occurrence

Comparison of the natural Sodium isotopes including isotopic abundance (mole fraction of the isotope mixture in percent):

	Atomic Mass m_a	Quantity	Half-life	Spin
Sodium Isotopic mixture	22.98976928 u	100 %
Isotope ²²Na	21.99443755(14) u	[trace]	2.6018(22) a	3+
Isotope ²³Na	22.98976928(2) u	100 %	stable	3/2+
Isotope ²⁴Na	23.990963012(18) u	[trace]	14.956(3) h	4+

Nuclear Isomers

Nuclear isomers or excited states with the activation energy in keV related to the ground state.

Nuclear Isomer	Excitation Energy	Half-life	Spin
^24mNa	472.2071(14) keV	20.18(10) ms	1+

Isotones and Isobars

The following table shows the atomic nuclei that are isotonic (same neutron number N = 13) and isobaric (same nucleon number A = 24) with Sodium-24. Naturally occurring isotopes are marked in green; light green = naturally occurring radionuclides.

Z	Isotone N = 13	Isobar A = 24
5	¹⁸B
6	¹⁹C
7	²⁰N	²⁴N
8	²¹O	²⁴O
9	²²F	²⁴F
10	²³Ne	²⁴Ne
11	²⁴Na	²⁴Na
12	²⁵Mg	²⁴Mg
13	²⁶Al	²⁴Al
14	²⁷Si	²⁴Si
15	²⁸P	²⁴P
16	²⁹S
17	³⁰Cl
18	³¹Ar
19	³²K

External data and identifiers

Adopted Levels, Gammas:NuDat 24Na

Literature and References

[1] - Enrico Fermi, Edoardo Amaldi, O. D'Agostino, F. Rasetti, E. Segrè:
Artificial radioactivity produced by neutron bombardment.
In: Proceedings of the Royal Society A, 146, 857, (1934), DOI 10.1098/rspa.1934.0168.

[2] - W. Rödel:
Sodium-24 produced by Cosmic Radiation.
In: Nature, 200, 999-1000, (1963), DOI 10.1038/200999b0.

[3] - Daniela Ekendahl et al.:
Neutron dose assessment using samples of human blood and hair.
In: Radiation Protection Dosimetry, 186, 2-3, 202-205, (2019), DOI 10.1093/rpd/ncz202.