Sodium-21

Properties and data of the isotope ²¹Na.

Contents

General Data

Radioactive Decay

Parent Nuclides

Isotones und Isobares

Literature

Sodium-21 is a radioisotope of the chemical element sodium, which, in addition to the element-specific 11 protons, has 10 neutrons in the atomic nucleus, resulting in the mass number 21. The very short-lived, unstable and therefore radioactive nuclide, which can only be produced artificially, has no practical significance; The study of ²¹Na serves exclusively academic purposes.

The isotope was first described in 1940 as a product of the irradiation of neon-20 enriched Ne gas with deuterons (hydrogen-2 nuclei, 2.6 MeV):

²⁰Ne(d,n)²¹Na [1].

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

General data

Name of the isotope:Sodium-21; Na-21Symbol:²¹Na or 2111NaMass number A:21 (= number of nucleons)Atomic number Z:11 (= number of protons)Neutrons N:10Isotopic mass:20.99765446(5) u (atomic weight of Sodium-21)Nuclide mass:20.9916201 u (calculated nuclear mass without electrons)Mass excess:-2.18486 MeVMass defect:0.175070052 u (per nucleus)Nuclear binding energy:163.07670302 MeV (per nucleus)
7.76555729 MeV (average binding energy per nucleon)Separation energy:S_N = 17.1067(11) MeV (first neutron)
S_P = 2.43190(4) MeV (first proton)Half-life:22.4615(39) sDecay constant λ:0.030859345126547 s^-1Specific activity α:9.291966159873 × 10⁺²⁰ Bq g^-1
25113422053.712 Ci g^-1Spin and parity:
(nuclear angular momentum)3/2+Magnetic dipole moment:μ(μ_N) = +2.38610(4)Quadrupole moment Q:+0.124(14) barn (100 fm²)Nuclear g-factor:g_l = 1.5907333333333Charge radius:3.0136(284) femtometer fmMirror nucleus:Neon-21Year of discovery:1940

Radioactive Decay

The half-life of the nuclide ²¹Na was redetermined in 2018 and used here. It replaces the previous value of T^1/2 = 22.49(4); In contrast, the new value is increased by 0.0049 s and the uncertainty is reduced by a factor of 1.5 [2].

Half-life T_½ = 22.4615(39) s respectively 2.24615 × 10¹ seconds s.

Decay mode	Daughter	Probability	Decay energy	γ energy (intensity)
β⁺	²¹Ne	100 %	3.54692(6) MeV

Parent Nuclides

Direct parent isotopes are: ²¹Mg, ²²Al, ²³Si.

Isotones and Isobars

The following table shows the atomic nuclei that are isotonic (same neutron number N = 10) and isobaric (same nucleon number A = 21) with Sodium-21. Naturally occurring isotopes are marked in green; light green = naturally occurring radionuclides.

Z	Isotone N = 10	Isobar A = 21
3	¹³Li
4	¹⁴Be
5	¹⁵B	²¹B
6	¹⁶C	²¹C
7	¹⁷N	²¹N
8	¹⁸O	²¹O
9	¹⁹F	²¹F
10	²⁰Ne	²¹Ne
11	²¹Na	²¹Na
12	²²Mg	²¹Mg
13	²³Al	²¹Al
14	²⁴Si
15	²⁵P
16	²⁶S

External data and identifiers

Adopted Levels, Gammas:NuDat 21Na

Literature and References

[1] - Ernest Pollard, William W. Watson:
Transmutation of the Separated Isotopes of Neon by Deuterons.
In: Physical Review, 58, 12, (1940), DOI 10.1103/PhysRev.58.12.

[2] - P. D. Shidling, R. S. Behling, B. Fenker et al.:
High-precision half-life measurement of the β⁺ decay of ²¹Na.
In: Physical Review C, 98, 015502, (2018), DOI 10.1103/PhysRevC.98.015502.

[3] - R. Bijker, F. Iachello:
Cluster structure of ²¹Ne and ²¹Na.
In: Nuclear Physics A, 1010, 122193, (2021), DOI 10.1016/j.nuclphysa.2021.122193.