Europium, 63Eu |
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| Pronunciation | (yuu-ROH-pee-əm) |
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| Appearance | silvery white, with a pale yellow tint; but rarely seen without oxide discoloration |
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| Atomic number (Z) | 63 |
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| Group | f-block groups (no number) |
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| Period | period 6 |
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| Block | f-block |
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| Electron configuration | [Xe] 4f7 6s2 |
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| Electrons per shell | 2, 8, 18, 25, 8, 2 |
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| Phase at STP | solid |
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| Melting point | 1099 K (826 °C, 1519 °F) |
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| Boiling point | 1802 K (1529 °C, 2784 °F) |
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| Density (at 20° C) | 5.246 g/cm3 |
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| when liquid (at m.p.) | 5.13 g/cm3 |
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| Heat of fusion | 9.21 kJ/mol |
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| Heat of vaporization | 176 kJ/mol |
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| Molar heat capacity | 27.66 J/(mol·K) |
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Vapor pressure
| P (Pa) |
1 |
10 |
100 |
1 k |
10 k |
100 k |
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863 |
957 |
1072 |
1234 |
1452 |
1796 |
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| Oxidation states | common: +2, +3
0 |
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| Electronegativity | Pauling scale: 1.2 |
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| Ionization energies | - 1st: 547.1 kJ/mol
- 2nd: 1085 kJ/mol
- 3rd: 2404 kJ/mol
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| Atomic radius | empirical: 180 pm |
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| Covalent radius | 198±6 pm |
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| Spectral lines of europium |
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| Natural occurrence | primordial |
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| Crystal structure | body-centered cubic (bcc) (cI2) |
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| Lattice constant | a = 458.22 pm (at 20 °C) |
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| Thermal expansion | 26.3×10−6/K (at 20 °C) |
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| Thermal conductivity | est. 13.9 W/(m⋅K) |
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| Electrical resistivity | poly: 0.900 µΩ⋅m (at r.t.) |
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| Magnetic ordering | paramagnetic |
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| Molar magnetic susceptibility | +34000.0×10−6 cm3/mol |
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| Young's modulus | 18.2 GPa |
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| Shear modulus | 7.9 GPa |
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| Bulk modulus | 8.3 GPa |
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| Poisson ratio | 0.152 |
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| Vickers hardness | 165–200 MPa |
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| CAS Number | 7440-53-1 |
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| Naming | after Europe |
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| Discovery | Eugène-Anatole Demarçay (1896) |
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| First isolation | 1937 |
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Europium is a chemical element; it has symbol Eu and atomic number 63. It is a silvery-white metal of the lanthanide series that reacts readily with air to form a dark oxide coating. Europium is the most chemically reactive, least dense, and softest of the lanthanides. It is soft enough to be cut with a knife. Europium was discovered in 1896, provisionally designated as Σ; in 1901, it was named after the continent of Europe. Europium usually assumes the oxidation state +3, like other members of the lanthanide series, but compounds having oxidation state +2 are also common. All europium compounds with oxidation state +2 are slightly reducing. Europium has no significant biological role and is relatively non-toxic compared to other heavy metals. Most applications of europium exploit the phosphorescence of europium compounds. Europium is one of the rarest of the rare-earth elements on Earth.