Actinium - Chemical Compounds

Chemical Compounds

Only a limited number of actinium compounds are known including AcF3, AcCl3, AcBr3, AcOF, AcOCl, AcOBr, Ac2S3, Ac2O3 and AcPO4. Except for AcPO4, they are all similar to the corresponding lanthanum compounds and contain actinium in the oxidation state +3. In particular, the lattice constants of the analogous lanthanum and actinium compounds differ by only a few percent.

Formula color symmetry space group No Pearson symbol a (pm) b (pm) c (pm) Z density,
g/cm3
Ac silvery fcc Fm3m 225 cF4 531.1 531.1 531.1 4 10.07
AcH2 cubic Fm3m 225 cF12 567 567 567 4 8.35
Ac2O3 white trigonal P3m1 164 hP5 408 408 630 1 9.18
Ac2S3 cubic I43d 220 cI28 778.56 778.56 778.56 4 6.71
AcF3 white hexagonal P3c1 165 hP24 741 741 755 6 7.88
AcCl3 hexagonal P63/m 165 hP8 764 764 456 2 4.8
AcBr3 white hexagonal P63/m 165 hP8 764 764 456 2 5.85
AcOF white cubic Fm3m 593.1 8.28
AcOCl tetragonal 424 424 707 7.23
AcOBr tetragonal 427 427 740 7.89
AcPO4ยท0.5H2O hexagonal 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.

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