Actinium

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Actinium

Atomic Mass	227
Electron Configuration	[Rn]7s26d1
Oxidation States	+3
Year Discovered	1899

Actinium

Atomic Mass	227
Electron Configuration	[Rn]7s26d1
Oxidation States	+3
Year Discovered	1899

Identifiers

Element Name	Actinium
Element Symbol	Ac
InChI	InChI=1S/Ac
InChIKey	QQINRWTZWGJFDB-UHFFFAOYSA-N

Properties

Atomic Weight	227 227 [227]
Electron Configuration	[Rn]7s²6d¹
Atomic Radius	Van der Waals Atomic Radius : 260 pm (Van der Waals) Empirical Atomic Radius : 195pm (Empirical) Covalent Atomic Radius : 215 pm (Covalent)
Oxidation States	+3 3, 2
Ground Level	²D_3/2
Ionization Energy	5.17 eV 5.380235 ± 0.000012 eV
Electronegativity	Pauling Scale Electronegativity : 1.1(Pauling Scale)
Atomic Spectra	Lines Holdings Levels Holdings
Physical Description	Solid
Element Classification	Metal
Element Period Number	7
Element Group Number	- Actinide
Density	10.07 grams per cubic centimeter
Melting Point	1324 K (1051°C or 1924°F) 1227°C
Boiling Point	3471 K (3198°C or 5788°F) 3198°C
Estimated Crustal Abundance	5.5×10^-10 milligrams per kilogram
Estimated Oceanic Abundance	Not Applicable

History

Actinium was discovered in 1899 by André-Louis Debierne, a French chemist, while experimenting with new methods of separating rare earth oxides. Friedrich Otto Giesel independently discovered actinium in 1902. Actinium is a rare element that is present in uranium ores in tiny amounts, but it is usually cheaper and easier to create actinium when it is needed by bombarding radium with neutrons in a nuclear reactor.

Actinium's most stable isotope, actinium-227, has a half-life of 21.77 years. It decays into francium-223 through alpha decay or into thorium-227 through beta decay.

From the Greek aktis, aktinos, meaning beam or ray. Discovered by Andre Debierne in 1899 and independently by F. Giesel in 1902. Occurs naturally in association with uranium minerals.

Description

Actinium-227, a decay product of uranium-235, is a beta emitter with a 21.6-year half-life. Its principal decay products are thorium-227 (18.5-day half-life), radium-223 (11.4-day half-life), and a number of short-lived products including radon, bismuth, polonium, and lead isotopes. In equilibrium with its decay products, it is a powerful source of alpha particles. Actinium metal has been prepared by the reduction of actinium fluoride with lithium vapor at about 1100 to 1300-degrees C. The chemical behavior of actinium is similar to that of the rare earths, particularly lanthanum. Purified actinium comes into equilibrium with its decay products at the end of 185 days, and then decays according to its 21.6-year half-life. It is about 150 times as active as radium, making it of value in the production of neutrons.

In April of 2012, Los Alamos National Laboratory announced a new medical isotope project that shows promise for rapidly producing major quantities of a new cancer-treatment agent, actinium 225 (Ac-225). Both a press release and a video are available.

Compounds

See more information at the Actinium compound page.

Element Forms

CID	Name	Formula	SMILES	Molecular Weight
23965	actinium	Ac	[Ac]	227.02775
167045	actinium-225	Ac	[225Ac]	225.02323
105152	actinium-227	Ac	[227Ac]	227.02775
105063	actinium-228	Ac	[228Ac]	228.03102
182609	actinium-226	Ac	[226Ac]	226.02610
167378	actinium-224	Ac	[224Ac]	224.02172
44154934	actinium-223	Ac	[223Ac]	223.01914

Isotopes

Stable Isotope Count	0

Isotopes in Earth/Planetary Science

227Ac (with a half-life of 21.77 years) has been used as a tracer of deep-sea mixing in the oceans. By determining concentrations of 227Ac in a water column, scientists can study the rates and patterns of mixing and other vertical exchange processes [583]. As a product of the 235U decay chain, 227Ac and other radioisotopes have been used to determine information about the movement of fluids in mid-oceanic ridges and basaltic melts [584], [585].

[583] W. Geibert, M. M. Rutgers van der Loeff, C. Hanfland, H. J. Dauelsberg. Earth. Planet. Sci. Lett.198, 147 (2002).

[584] D. McKenzie. Chem. Geol.162, 81 (2000).

[585] W. S. Moore, W. Ussler III, C. K. Paull. Mar. Chem.109, 421 (2008).

Isotopes in Medicine

225Ac (with a half-life of 10 days) can be used in cancer treatments (Fig. IUPAC.89.1). The isotope is attached to a chelating agent (a substance that can form multiple bonds to a single metal ion) and delivered to the problem site. The emissions of alpha particles from actinium and its daughter products cause tumor death [586]. 225Ac in a series of alpha decays produces 213Bi (with a half-life of 0.76 h), which is also used for radioimmunotherapy [587].

Fig. IUPAC.89.1: The Medical Actinium for Therapeutic Treatment (MATT) is a separations process that recovers ²²⁵Ac from unused nuclear fuel so the isotope can be used in cancer treatment and research. (Image Source: Idaho National Laboratory) [588].

[586] M. R. McDevitt, D. Ma, L. T. Lai, J. Simon, P. Borchardt, R. K. Frank, K. Wu, V. Pellegrini, M. J. Curcio, M. Miederer, N. H. Bander, D. A. Scheinberg. Science294, 1537 (2001).

[587] D. Ma, M. R. McDevitt, R. D. Finn, D. A. Scheinberg. Appl. Radiat. Isot.55, 667 (2001).

[588] Idaho National Laboratory. INL Wins Two Idaho Innovation Awards for Bioscience and Computer Software, Idaho National Laboratory (2017), April 8; https://public.inl.gov/features_archive/Shared%20Documents/62290_inl_wins_two_idaho_innovation_awards_for_bioscience_and_computer_software.pdf.

Isotopes Used as a Source of Radioactive Isotope(s)

225Ac, which is a pure alpha emitter, is used to produce 213Bi with an 225Ac/ 213Bi radionuclide generator (Fig. IUPAC.89.2). 213Bi is a mixed alpha and beta emitter. The primary mode of decay is by beta emission to the very short-lived, alpha emitter 213Po. The 8.4 MeV alpha particle emitted by 213Po has a path length of 76 μm in human tissue and is responsible for its cytotoxic effects.

Fig. IUPAC.89.2: Institute for Transuranium Elements (ITU) Standard ²²⁵Ac/ ²¹³Bi Radionuclide Generator. Image kindly provided by Dr. Alfred Morgenstern, European Commission, Joint Research Centre – Institute for Transuranium Elements, Karlsruhe, Germany.

Isotope Mass and Abundance

Isotope	Atomic Mass (uncertainty) [u]	Abundance (uncertainty)
²²⁷Ac	227.0277523(25)

Atomic Mass, Half Life, and Decay

Nuclide	Atomic Mass and Uncertainty [u]	Half Life and Uncertainty	Discovery Year	Decay Modes, Intensities and Uncertainties [%]
²⁰⁵Ac	205.015144152 ± 0.000063682	80 ms ± 60	2014	α≈100%; β⁺ ?
²⁰⁶Ac	206.014476477 ± 0.000069874	25 ms ± 7	1998	α≈100%; β⁺ ?
²⁰⁶Ac^m	206.014476477 ± 0.000069874	41 ms ± 16	1996	α≈100%; β⁺ ?
²⁰⁷Ac	207.011965967 ± 0.000060384	31 ms ± 8	1994	α≈100%
²⁰⁸Ac	208.011552251 ± 0.000069225	97 ms ± 15	1994	α≈100%; β⁺ ?
²⁰⁸Ac^m	208.011552251 ± 0.000069225	28 ms ± 7	1994	α≈100%; IT ?; β⁺ ?
²⁰⁹Ac	209.009495375 ± 0.000059953	94 ms ± 10	1968	α≈100%; β⁺ ?
²¹⁰Ac	210.009408625 ± 0.000066782	350 ms ± 40	1968	α≈100%; β⁺ ?
²¹¹Ac	211.007668846 ± 0.000057706	213 ms ± 25	1968	α≈100%; β⁺ ?
²¹²Ac	212.007836442 ± 0.000023492	895 ms ± 28	1968	α≈100%; β⁺ ?
²¹³Ac	213.006592665 ± 0.000012522	738 ms ± 16	1968	α≈100%; β⁺ ?
²¹⁴Ac	214.006906400 ± 0.000014547	8.2 s ± 0.2	1968	α=93±0.4%; β⁺=7±0.4%
²¹⁵Ac	215.006474061 ± 0.000013318	171 ms ± 10	1968	α≈100%; β⁺=0.09±0.2%
²¹⁵Ac^m	215.006474061 ± 0.000013318	185 ns ± 30	1983	IT=100%
²¹⁵Acⁿ	215.006474061 ± 0.000013318	335 ns ± 10	1983	IT=100%
²¹⁶Ac	216.008749101 ± 0.000009908	440 us ± 16	1967	α=100%; β⁺ ?
²¹⁶Ac^m	216.008749101 ± 0.000009908	441 us ± 7	1966	α=100%; β⁺ ?
²¹⁶Acⁿ	216.008749101 ± 0.000009908	~300 ns	2006	IT=100%
²¹⁷Ac	217.009342325 ± 0.000012048	69 ns ± 4	1972	α≈100%; β⁺ ?
²¹⁷Ac^m	217.009342325 ± 0.000012048	740 ns ± 40	1973	IT=95.49±1.8%; α=4.51±1.8%
²¹⁸Ac	218.011648860 ± 0.000061853	1.00 us ± 0.04	1970	α=100%
²¹⁸Ac^m	218.011648860 ± 0.000061853	>100 ns [Estimated]		IT ?; α ?; β⁺ ?
²¹⁸Acⁿ	218.011648860 ± 0.000061853	103 ns ± 11	1994	IT=100%
²¹⁹Ac	219.012420425 ± 0.000055263	9.4 us ± 1.0	1970	α=100%; β⁺ ?
²²⁰Ac	220.014754527 ± 0.000006579	26.36 ms ± 0.19	1970	α=100%; β⁺ ?
²²¹Ac	221.015599721 ± 0.000061086	52 ms ± 2	1968	α=100%
²²²Ac	222.017844232 ± 0.000005044	5.0 s ± 0.5	1949	α=99±0.1%; β⁺=1±0.1%
²²²Ac^m	222.017844232 ± 0.000005044	1.05 m ± 0.05	1972	α≈98.6±0.4%; β⁺≈1.4±0.4%; IT ?
²²³Ac	223.019135982 ± 0.000007457	2.10 m ± 0.05	1948	α≈99%; ε ?
²²⁴Ac	224.021722249 ± 0.000004389	2.78 h ± 0.16	1948	β⁺=90.5±1.7%; α=9.5±1.7%; β^- ?
²²⁵Ac	225.023228601 ± 0.000005107	9.9190 d ± 0.0021	1947	α=100%; 14C=5.3e-10±1.3%
²²⁶Ac	226.026096999 ± 0.000003327	29.37 h ± 0.12	1950	β^-=83±0.3%; ε=17±0.3%; α=0.006±0.2%
²²⁷Ac	227.027750594 ± 0.000002068	21.772 y ± 0.003	1851	β^-=98.62±3.6%; α=1.38±3.6%
²²⁸Ac	228.031019685 ± 0.000002247	6.15 h ± 0.02	1908	β^-=100%
²²⁸Ac^m	228.031019685 ± 0.000002247	180 s ± 70	2008	IT ?; β^- ?
²²⁹Ac	229.032947000 ± 0.000013	62.7 m ± 0.5	1952	β^-=100%
²³⁰Ac	230.036327000 ± 0.000017	122 s ± 3	1973	β^-=100%; β^-SF=1.2e-6±0.4%
²³¹Ac	231.038393000 ± 0.000014	7.5 m ± 0.1	1973	β^-=100%
²³²Ac	232.042034000 ± 0.000014	1.98 m ± 0.08	1986	β^-=100%
²³³Ac	233.044346000 ± 0.000014	143 s ± 10	1983	β^-=100%
²³⁴Ac	234.048139000 ± 0.000015	45 s ± 2	1986	β^-=100%
²³⁴Ac^m	234.048139000 ± 0.000015	>93 s	2008	β^- ?; IT ?
²³⁴Acⁿ	234.048139000 ± 0.000015	180 s ± 70	2008	β^- ?; IT ?
²³⁵Ac	235.050840000 ± 0.000015	62 s ± 4	2006	β^-=100%
²³⁶Ac	236.054988000 ± 0.000041	4.5 m ± 3.6	2010	β^-=100%
²³⁷Ac	237.057993 ± 0.000429 [Estimated]	23 s [Estimated]		β^- ?

Information Sources

Actinium

View products including Actinium ➡︎

Identifiers

Properties

History

Description

Users

Compounds

Element Forms

Isotopes

Isotopes in Earth/Planetary Science

Isotopes in Medicine

Isotopes Used as a Source of Radioactive Isotope(s)

Isotope Mass and Abundance

Atomic Mass, Half Life, and Decay

Information Sources