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Pronunciation | (ak-TIN-ee-əm) |
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Appearance | silvery-white, glowing with an eerie blue light; sometimes with a golden cast |
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Mass number | 227 (most stable isotope) |
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Atomic number (Z) | 89 |
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Group | group 3 |
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Period | period 7 |
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Block | f-block |
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Electron configuration | [Rn] 6d1 7s2 |
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Electrons per shell | 2, 8, 18, 32, 18, 9, 2 |
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Phase at STP | Ac: Solid |
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Melting point | 1500 K (1227 °C, 2240 °F) (estimated) |
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Boiling point | 3500±300 K (3200±300 °C, 5800±500 °F) (extrapolated) |
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Density (near r.t.) | 10 g/cm3 |
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Heat of fusion | 14 kJ/mol |
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Heat of vaporization | 400 kJ/mol |
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Molar heat capacity | 27.2 J/(mol·K) |
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Oxidation states | +2, +3 (a strongly basic oxide) |
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Electronegativity | Pauling scale: 1.1 |
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Ionization energies | - 1st: 499 kJ/mol
- 2nd: 1170 kJ/mol
- 3rd: 1900 kJ/mol
- (more)
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Covalent radius | 215 pm |
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Spectral lines of actinium |
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Natural occurrence | Ac: From decay |
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Crystal structure | face-centered cubic (fcc) |
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Thermal conductivity | 12 W/(m·K) |
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CAS Number | 7440-34-8 |
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Discovery and first isolation | Friedrich Oskar Giesel (1902) |
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Named by | André-Louis Debierne (1899) |
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| references |