71LuLutetium174.9668 u
Lutetium (Lu)
Lutetium is a lanthanide with atomic number 71, in period 6 of the periodic table. Its atomic mass is 174.9668 u and its electron configuration is [Xe] 4f¹⁴ 5d¹ 6s². Solid at 25 °C.
Key facts
| Atomic number | 71 |
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| Atomic mass | 174.9668 u |
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| Category | Lanthanide |
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| Period | 6 |
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| Group | --- |
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| Block | d |
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| Electron configuration | [Xe] 4f¹⁴ 5d¹ 6s² |
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| Electrons per shell | 2, 8, 18, 32, 9, 2 |
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| Electronegativity (Pauling) | 1.27 |
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| Oxidation states | +2, +3common in bold |
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| State at 25 °C | Solid |
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| Melting point | 1936 K1662.85 °C |
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| Boiling point | 3675 K3401.85 °C |
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| Density | 9.841 g/cm³ |
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Atomic properties
| First ionization energy | 5.426 eV |
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| Electron affinity | 50 kJ/mol |
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| Atomic radius | 175 pm |
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| Covalent radius | 187 pm |
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| Van der Waals radius | 221 pm |
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| Common ions | Lu³⁺ |
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| Protons, neutrons, electrons | 71, 104, 71 |
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Physical and thermal properties
| Molar volume | 17.78 cm³/mol |
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| Heat of fusion | 22 kJ/mol |
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| Heat of vaporization | 415 kJ/mol |
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| Specific heat | 154 J/(kg·K) |
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| Thermal conductivity | 16 W/(m·K) |
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| Thermal expansion | 1 × 10⁻⁵ K⁻¹ |
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| Mohs hardness | 2.6 |
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| Young’s modulus | 67 GPa |
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| Crystal structure | Simple hexagonal |
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| Magnetic type | Paramagnetic |
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Identification and history
| CAS number | 7439-94-3 |
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| Latin name | Lutetium |
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| Discovered by | C. Welsbach, G. Urbain · 1907 |
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| Named by | --- |
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Natural isotopes
| Isotope | Mass (u) | Abundance |
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| 175Lu | 174.940777 | 97.401 % |
| 176Lu | 175.942692 | 2.599 % |
Data checked against PubChem (NIH), IUPAC, the NIST Atomic Spectra Database and the IAEA (NUBASE and AME), the same data you see in the app.
A dash (---) means there is no reliable published measurement. The app never makes one up.
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Periodic Table