![](//upload.wikimedia.org/wikipedia/commons/thumb/b/bb/Thallium_pieces_in_ampoule.jpg/220px-Thallium_pieces_in_ampoule.jpg) |
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Pronunciation | (THAL-ee-əm) |
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Appearance | silvery white |
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| [204.382, 204.385][1] |
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Atomic number (Z) | 81 |
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Group | group 13 (boron group) |
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Period | period 6 |
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Block | p-block |
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Electron configuration | [Xe] 4f14 5d10 6s2 6p1 |
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Electrons per shell | 2, 8, 18, 32, 18, 3 |
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Phase at STP | solid |
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Melting point | 577 K (304 °C, 579 °F) |
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Boiling point | 1746 K (1473 °C, 2683 °F) |
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Density (near r.t.) | 11.85 g/cm3 |
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when liquid (at m.p.) | 11.22 g/cm3 |
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Heat of fusion | 4.14 kJ/mol |
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Heat of vaporization | 165 kJ/mol |
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Molar heat capacity | 26.32 J/(mol·K) |
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Vapor pressure
P (Pa) |
1 |
10 |
100 |
1 k |
10 k |
100 k |
at T (K) |
882 |
977 |
1097 |
1252 |
1461 |
1758 |
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Oxidation states | −5,[2] −2, −1, +1, +2, +3 (a mildly basic oxide) |
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Electronegativity | Pauling scale: 1.62 |
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Ionization energies | - 1st: 589.4 kJ/mol
- 2nd: 1971 kJ/mol
- 3rd: 2878 kJ/mol
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Atomic radius | empirical: 170 pm |
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Covalent radius | 145±7 pm |
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Van der Waals radius | 196 pm |
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Spectral lines of thallium |
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Natural occurrence | primordial |
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Crystal structure | hexagonal close-packed (hcp) |
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Speed of sound thin rod | 818 m/s (at 20 °C) |
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Thermal expansion | 29.9 µm/(m⋅K) (at 25 °C) |
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Thermal conductivity | 46.1 W/(m⋅K) |
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Electrical resistivity | 0.18 µΩ⋅m (at 20 °C) |
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Magnetic ordering | diamagnetic[3] |
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Molar magnetic susceptibility | −50.9×10−6 cm3/mol (298 K)[4] |
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Young's modulus | 8 GPa |
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Shear modulus | 2.8 GPa |
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Bulk modulus | 43 GPa |
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Poisson ratio | 0.45 |
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Mohs hardness | 1.2 |
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Brinell hardness | 26.5–44.7 MPa |
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CAS Number | 7440-28-0 |
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Naming | after Greek thallos, green shoot or twig |
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Discovery | William Crookes (1861) |
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First isolation | Claude-Auguste Lamy (1862) |
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Category: Thallium | references |