|Name , symbol , atomic number||Actinium, Ac, 89|
|Element category||Transition metals|
|Group , period , block||3 , 7 , d|
|Mass fraction of the earth's envelope||6 · 10 −14 ppm|
|Atomic mass||227.0278 u|
|Atomic radius||195 pm|
|Covalent radius||215 pm|
|Electron configuration||[ Rn ] 6 d 1 7 s 2|
|1. Ionization energy||5.380 226 (24) eV ≈ 519.11 kJ / mol|
|2. Ionization energy||11.75 (3) eV ≈ 1 134 kJ / mol|
|3. Ionization energy||17th.431 (20) eV ≈ 1 682 kJ / mol|
|4. Ionization energy||44.8 (1.4 eV) ≈ 4 320 kJ / mol|
|5. Ionization energy||55.0 (1.9) eV ≈ 5 310 kJ / mol|
|Crystal structure||Cubic area-centered|
|density||10.07 g / cm 3|
|Melting point||1323 K (1050 ° C)|
|boiling point||3573 (3300 ° C)|
|Molar volume||22.55 · 10 −6 m 3 · mol −1|
|Heat of evaporation||400 kJ / mol|
|Heat of fusion||14 kJ mol −1|
|Thermal conductivity||12 W m −1 K −1|
|Normal potential||−2.13 V
(Ac 3+ + 3 e - → Ac)
|Electronegativity||1.1 ( Pauling scale )|
|For other isotopes see list of isotopes|
|Hazard and safety information|
As far as possible and customary, SI units are used.
Unless otherwise noted, the data given apply to standard conditions .
Actinium is a radioactive chemical element with the element symbol Ac and the atomic number 89. In the periodic table of the elements it is in the 3rd IUPAC group , the scandium group . The element is a metal and belongs to the 7th period , d-block . It is the namesake of the group of actinides , the 14 elements that follow it.
Actinium was discovered in 1899 by the French chemist André-Louis Debierne , who isolated it from pitchblende and initially attributed similarities to titanium or thorium ; He derived his name from the Greek ἀκτίς aktís 'beam' because of the radioactivity . Friedrich Giesel discovered the element independently in 1902 and described a similarity to lanthanum ; he gave it the name Emanium , a formation from the Latin emano “ to flow out”, also with reference to the emitted radiation. After Actinium and Emanium were recognized as identical in 1904, Debierne's naming was given preference since he first discovered it.
The history of the discovery was still described as questionable in publications from 1971 and later in 2000. They show that the publications of 1904 on the one hand and those of 1899 and 1900 on the other hand show contradictions.
Extraction and presentation
- The times given are half-lives .
The metal is shiny silver-white and relatively soft. Due to its strong radioactivity, Actinium glows in a light blue light in the dark.
Actinium is the eponymous element of the actinides , similar to lanthanum for the lanthanoids . The group of elements shows more distinct differences than the lanthanoids; therefore it was not until 1945 that Glenn T. Seaborg was able to suggest the most important changes to Mendeleev's periodic table: the introduction of actinides.
It is very reactive and can be attacked by air and water, but is covered with a layer of actinium oxide, which protects it from further oxidation. The Ac 3+ ion is colorless. Actinium's chemical behavior is very similar to that of lanthanum . Actinium is trivalent in all ten known compounds.
26 isotopes are known , only two of which occur naturally. The longest-lived isotope 227 Ac ( half-life 21.8 years) has two decay channels : it is an alpha and a beta emitter . 227 Ac is a decay product of the uranium isotope 235 U and occurs to a small extent in uranium ores. From this a weighable amount of 227 Ac can be obtained, which thus enables a relatively simple study of this element. Since there are some gamma emitters among the radioactive decay products , complex radiation protection precautions are necessary.
During the dual decay of 227 Ac, the largest part goes into the thorium isotope 227 Th with emission of beta particles , but approx. 1% decays through alpha emission to Francium 223 Fr. A solution of 227 Ac is therefore a source for the short-lived 223 Fr can be used. The latter can then be separated and examined regularly.
Classifications according to the CLP regulation are not available because they only include chemical hazard and play a completely subordinate role compared to the hazards based on radioactivity . The latter also only applies if the amount of substance involved is relevant.
Only a small number of actinium compounds are known. With the exception of AcPO 4 , they are all similar to the corresponding lanthanum compounds and contain actinium in the +3 oxidation state. In particular, the lattice constants of the respective lanthanum and actinium compounds differ only in a few percent.
|formula||colour||symmetry||Space group||Pearson symbol||a (pm)||b (pm)||c (pm)||Z||Density,
g / cm 3
|Ac||silver||fcc||Fm 3 m (No. 225)||cF4||531.1||531.1||531.1||4th||10.07|
|AcH 2||cubic||Fm 3 m (No. 225)||cF12||567||567||567||4th||8.35|
|Ac 2 O 3||White||trigonal||P 3 m 1 (No. 164)||hP5||408||408||630||1||9.18|
|Ac 2 S 3||cubic||I 4 3 d (No. 220)||cI28||778.56||778.56||778.56||4th||6.71|
|AcF 3||White||hexagonal||P 3 c 1 (No. 165)||hP24||741||741||755||6th||7.88|
|AcCl 3||hexagonal||P 6 3 / m (No. 176)||hP8||764||764||456||2||4.8|
|AcBr 3||White||hexagonal||P 6 3 / m (No. 176)||hP8||764||764||456||2||5.85|
|AcOF||White||cubic||Fm 3 m (No. 225)||593.1||8.28|
|AcPO 4 • 0.5H 2 O||hexagonal||721||721||664||5.48|
Actinium (III) oxide (Ac 2 O 3 ) can be obtained by heating the hydroxide at 500 ° C or the oxalate at 1100 ° C in vacuo. The crystal lattice is isotypic with the oxides of most trivalent rare earth metals .
Actinium (III) fluoride (AcF 3 ) can be prepared either in solution or by solid reaction. In the first case, hydrofluoric acid is added to an Ac 3+ solution at room temperature and the product is precipitated. in the other case actinium metal is treated with hydrogen fluoride at 700 ° C in a platinum apparatus.
If sodium dihydrogen phosphate (NaH 2 PO 4 ) is added to a solution of actinium in hydrochloric acid, white-colored actinium phosphate (AcPO 4 · 0.5 H 2 O) is obtained; Heating actinium (III) oxalate with hydrogen sulfide at 1400 ° C for a few minutes results in black actinium (III) sulfide (Ac 2 S 3 ).
- Harold W. Kirby, Lester R. Morss: Actinium , in: Lester R. Morss, Norman M. Edelstein, Jean Fuger (Eds.): The Chemistry of the Actinide and Transactinide Elements , Springer, Dordrecht 2006; ISBN 1-4020-3555-1 , pp. 18-51 ( doi: 10.1007 / 1-4020-3598-5_2 ).
- Harry H. Binder: Lexicon of the chemical elements , S. Hirzel Verlag, Stuttgart 1999, ISBN 3-7776-0736-3 .
- The values for the properties (info box) are taken from www.webelements.com (Actinium) , unless otherwise stated .
- entry on actinium in Kramida, A., Ralchenko, Yu., Reader, J. and NIST ASD Team (2019): NIST Atomic Spectra Database (ver. 5.7.1) . Ed .: NIST , Gaithersburg, MD. doi : 10.18434 / T4W30F ( https://physics.nist.gov/asd ). Retrieved June 13, 2020.
- entry on actinium at WebElements, https://www.webelements.com , accessed on June 13, 2020.
- The hazards emanating from radioactivity do not belong to the properties to be classified according to the GHS labeling. With regard to other hazards, this element has either not yet been classified or a reliable and citable source has not yet been found.
- André-Louis Debierne: "Sur une nouvelle matière radio-active", in: Comptes rendus , 1899 , 129 , pp. 593-595 ( digitized on Gallica ).
- André-Louis Debierne: "Sur un nouvel élément radio-actif: l'actinium", in: Comptes rendus , 1900 , 130 , pp. 906-908 ( digitized on Gallica ).
- N. A. Figurowski, The discovery of the chemical elements and the origin of their names , in German translation by Leo Korniljew / Ernst Lemke, Moscow 1981, ISBN 3-7614-0561-8 , p. 64.
- Friedrich Oskar Giesel: "About radium and radioactive substances", in: Reports of the German Chemical Society , 1902 , 35 (3), pp. 3608-3611 ( doi: 10.1002 / cber.190203503187 ).
- Friedrich Oskar Giesel: "Ueber den Emanationskörper (Emanium)", in: Reports of the German Chemical Society , 1904 , 37 (2), pp. 1696-1699 ( doi: 10.1002 / cber.19040370280 ).
- Friedrich Oskar Giesel: "Ueber Emanium", in: Reports of the German Chemical Society , 1905 , 38 (1), pp. 775-778 ( doi: 10.1002 / cber.190503801130 ).
- HW Kirby: "The Discovery of Actinium", in: Isis , 1971 , 62 (3), pp. 290-308 ( JSTOR 229943 ).
- JP Adloff: "The centenary of a controversial discovery: actinium", in: Radiochim. Acta , 2000 , 88 , p. 123 ( doi: 10.1524 / ract.2000.88.3-4.123 ).
- Joseph G. Stites, Murrell L. Salutsky, Bob D. Stone: "Preparation of Actinium Metal", in: J. Am. Chem. Soc. , 1955 , 77 (1), pp. 237-240 ( doi: 10.1021 / ja01606a085 ).
- Frederick Seitz, David Turnbull: Solid state physics: advances in research and applications , Academic Press, 1964, ISBN 0-12-607716-9 , pp. 289-291 ( limited preview in the Google book search).
- Glenn T. Seaborg: "The Transuranium Elements", in: Science , 1946 , 104 , No. 2704, pp. 379-386 ( doi: 10.1126 / science.104.2704.379 ; PMID 17842184 ).
- JJ Katz, WM Manning: “Chemistry of the Actinide Elements”, in: Annual Review of Nuclear Science , 1952 , 1 , pp. 245-262 ( doi: 10.1146 / annurev.ns.01.120152.001333 ).
- Sherman Fried, French Hagemann, WH Zachariasen: “The Preparation and Identification of Some Pure Actinium Compounds”, in: J. Am. Chem. Soc. , 1950 , 72 , pp. 771-775 ( doi: 10.1021 / ja01158a034 ).
- J. D. Farr, AL Giorgi, MG Bowman, RK Money: "The crystal structure of actinium metal and actinium hydride", in: Journal of Inorganic and Nuclear Chemistry , 1961 , 18 , pp. 42-47 ( doi: 10.1016 / 0022-1902 (61) 80369-2 ).
- W. H. Zachariasen: "Crystal Chemical Studies of the 5 f Series of Elements. XII. New Compounds Representing Known Structure Types ", in: Acta Crystallographica , 1949 , 2 , pp. 388-390 ( doi: 10.1107 / S0365110X49001016 ).
- WH Zachariasen: "Crystal Chemical Studies of the 5 f Series of Elements. VI. The Ce 2 S 3 - Ce 3 S 4 Type of Structure ", in: Acta Crystallographica , 1949 , 2 , pp. 57-60 ( doi: 10.1107 / S0365110X49000126 ).
- Gerd Meyer, Lester R. Morss: Synthesis of lanthanide and actinide compounds , Springer, 1991, ISBN 0-7923-1018-7 , p. 71 ( limited preview in Google book search).
- W. H. Zachariasen: "Crystal Chemical Studies of the 5 f Series of Elements. I. New Structure Types ", in: Acta Crystallographica , 1948 , 1 , pp. 265-268 ( doi: 10.1107 / S0365110X48000703 ).
- Gerd Meyer, Lester R. Morss: Synthesis of lanthanide and actinide compounds , Springer, 1991, ISBN 0-7923-1018-7 , pp. 87-88 ( limited preview in Google book search).