Radium-226

Properties and data of the isotope ²²⁶Ra.

Contents

General Data

Radioactive Decay

Radiation emissions

Parent Nuclides

Isotones und Isobares

Literature

The radioisotope radium-226, with a half-life of 1,600 years, is the most stable nuclide of the chemical element radium. The atomic nucleus consists of 88 protons, which are characteristic of the element, and 138 neutrons; This results in a mass number of 226.

²²⁶Ra occurs in the natural decay chain (4n + 2) from uranium-238, which is called the uranium series and sometimes the radium series.

Radium-226 is essentially only found in pitchblende (uraninite; uranium pitch ore); Some uranium ores, such as the carnotide K₂(UO₂)₂[V₂O₈] × 3 H₂O, contain even smaller amounts.

Radium is currently no longer produced. Amounts required for medical and other research purposes come from historical production, which produced around 2.5 kg of radium-226 from uranium ores between 1902 and 1954 [see. Marx, 2014].

General data

Name of the isotope:Radium-226; Ra-226Symbol:²²⁶Ra or 22688RaMass number A:226 (= number of nucleons)Atomic number Z:88 (= number of protons)Neutrons N:138Isotopic mass:226.0254082(21) u (atomic weight of Radium-226)Nuclide mass:225.9771392 u (calculated nuclear mass without electrons)Mass excess:23.66759 MeVMass defect:1.858953024 u (per nucleus)Nuclear binding energy:1731.60358814 MeV (per nucleus)
7.66196278 MeV (average binding energy per nucleon)Separation energy:S_N = 6.3966(28) MeV (first neutron)
S_P = 7.442(12) MeV (first proton)Cross section:σ(n.γ) = 13 barn (thermal neutron capture cross-section)Half-life:1600(7) aDecay constant λ:1.373722056855 × 10^-11 s^-1Specific activity α:36605078445.956 Bq g^-1
0.9893264444853 Ci g^-1Spin and parity:
(nuclear angular momentum)0+Charge radius:5.7211(288) femtometer fmYear of discovery:1898

Radioactive Decay

Half-life T_½ = 1600(7) a respectively 5.045760 × 10¹⁰ seconds s.

Decay mode	Daughter	Probability	Decay energy
α	²²²Rn		4.87070(25) MeV
CD	²¹²Pb	-	-
+	¹⁴C	-	-

Radium-226 decays to Radon-222, emitting α-particles with an energy of 4.87 MeV and gamma radiation [186.211(13) keV, intensity 3.64(4) %]. The cross section is σ(n,γ) = 12.8 barn. In addition, a very rare cluster decay to carbon-14 and lead-212 was observed.

The radioactive decay of pure radium releases an energy output of 28 W/kg; This quickly increases to 160 W/kg within a few days through the establishment of a secular equilibrium with the short-lived and highly radioactive degradation products.

Parent Nuclides

Direct parent isotopes are: ²³⁰Th, ²²⁶Ac, ²²⁶Fr.

Occurrence

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

	Atomic Mass m_a	Quantity	Half-life	Spin
Radium Isotopic mixture	226.025409353 u	100 %
Isotope ²²⁶Ra	226.0254082(21) u	100 %	1600(7) a	0+

Isotones and Isobars

The following table shows the atomic nuclei that are isotonic (same neutron number N = 138) and isobaric (same nucleon number A = 226) with Radium-226. Naturally occurring isotopes are marked in green; light green = naturally occurring radionuclides.

Z	Isotone N = 138	Isobar A = 226
82	²²⁰Pb
83	²²¹Bi
84	²²²Po	²²⁶Po
85	²²³At	²²⁶At
86	²²⁴Rn	²²⁶Rn
87	²²⁵Fr	²²⁶Fr
88	²²⁶Ra	²²⁶Ra
89	²²⁷Ac	²²⁶Ac
90	²²⁸Th	²²⁶Th
91	²²⁹Pa	²²⁶Pa
92	²³⁰U	²²⁶U
93	²³¹Np	²²⁶Np
94	²³²Pu
95	²³³Am
96	²³⁴Cm
97	²³⁵Bk

External data and identifiers

CAS:13982-63-3InChI Key:HCWPIIXVSYCSAN-IGMARMGPSA-NSMILES:[226Ra]PubChem:ID 9877911Adopted Levels, Gammas:NuDat 226Ra

Literature and References

[1] - Sebastian Markus Marx:
Radium-Aufreinigung zur Herstellung von Actinium-225 am Zyklotron für die Alpha-Immuntherapie.
In: Dissertation, TU München, (2014).

[2] - A. Soylu, S. Evlice:
Deformation effects on cluster decays of radium isotopes.
In: Nuclear Physics A, (2015), DOI 10.1016/j.nuclphysa.2015.01.008.