Actinium compounds

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Actinium compounds are compounds containing the element

Ac2O3, AcPO4 and Ac(NO3)3. Except for AcPO4, they are all similar to the corresponding lanthanum compounds. They all contain actinium in the oxidation state +3.[1][2] In particular, the lattice constants of the analogous lanthanum and actinium compounds differ by only a few percent.[2]

Properties of actinium compounds

Formula color symmetry space group No Pearson symbol a (pm) b (pm) c (pm) Z density,
g/cm3
Ac silvery fcc[3] Fm3m 225 cF4 531.1 531.1 531.1 4 10.07
AcH2 unknown cubic[3] Fm3m 225 cF12 567 567 567 4 8.35
Ac2O3 white[4]
trigonal[5]
 P3m1 164 hP5 408 408 630 1 9.18
Ac2S3 black cubic[6] I43d 220 cI28 778.56 778.56 778.56 4 6.71
AcF3 white[7]
hexagonal[2][5]
 P3c1 165 hP24 741 741 755 6 7.88
AcCl3 white hexagonal[2][8] P63/m 165 hP8 764 764 456 2 4.8
AcBr3 white[2] hexagonal[8] P63/m 165 hP8 764 764 456 2 5.85
AcOF white[9] cubic[2] Fm3m 593.1 8.28
AcOCl white tetragonal[2] 424 424 707 7.23
AcOBr white tetragonal[2] 427 427 740 7.89
AcPO4·0.5H2O unknown hexagonal[2] 721 721 664 5.48

Here a, b and c are lattice constants, No is space group number and Z is the number of formula units per unit cell. Density was not measured directly but calculated from the lattice parameters.

Oxides

Main article: Actinium(III) oxide

lanthanum(III) oxide. It can be obtained by heating the hydroxide at 500 °C or the oxalate at 1100 °C, in vacuum. Its crystal lattice is isotypic with the oxides of most trivalent rare-earth metals.[2]

Halides

oxyfluoride AcOF. Whereas lanthanum oxyfluoride can be easily obtained by burning lanthanum trifluoride in air at 800 °C for an hour, similar treatment of actinium trifluoride yields no AcOF and only results in melting of the initial product.[2][9]

AcF3 + 2 NH3 + H2O → AcOF + 2 NH4F

Actinium trichloride is obtained by reacting actinium hydroxide or

ammonium hydroxide at 1000 °C. However, in contrast to the oxyfluoride, the oxychloride could well be synthesized by igniting a solution of actinium trichloride in hydrochloric acid with ammonia.[2]

Reaction of aluminium bromide and actinium oxide yields actinium tribromide:

Ac2O3 + 2 AlBr3 → 2 AcBr3 + Al2O3

and treating it with ammonium hydroxide at 500 °C results in the oxybromide AcOBr.[2]

Other compounds

Actinium hydride was obtained by reduction of actinium trichloride with potassium at 300 °C, and its structure was deduced by analogy with the corresponding LaH2 hydride. The source of hydrogen in the reaction was uncertain.[11]

Mixing

actinium oxide at 1000 °C.[2]

See also

References

  1. ^ a b Actinium, Great Soviet Encyclopedia (in Russian)
  2. ^
    doi:10.1021/ja01158a034
    .
  3. ^
    OSTI 4397640
    .
  4. doi:10.1021/ja01606a085
    .
  5. ^
    doi:10.1107/S0365110X49001016
    .
  6. doi:10.1107/S0365110X49000126. Archived
    (PDF) from the original on 2022-10-09.
  7. ^ Meyer, p. 71
  8. ^
    doi:10.1107/S0365110X48000703
    .
  9. ^ a b Meyer, pp. 87–88
  10. doi:10.1021/ja01158a034
    .
  11. ^ Meyer, p. 43
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