76OsOsmium190.23 u
Osmium (Os)
Osmium is a transition metal with atomic number 76, in period 6 and group 8 of the periodic table. Its atomic mass is 190.23 u and its electron configuration is [Xe] 4f¹⁴ 5d⁶ 6s². Solid at 25 °C.
Key facts
| Atomic number | 76 |
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| Atomic mass | 190.23 u |
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| Category | Transition Metal |
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| Period | 6 |
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| Group | 8 |
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| Block | d |
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| Electron configuration | [Xe] 4f¹⁴ 5d⁶ 6s² |
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| Electrons per shell | 2, 8, 18, 32, 14, 2 |
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| Electronegativity (Pauling) | 2.2 |
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| Oxidation states | −2, −1, +1, +2, +3, +4, +5, +6, +7, +8common in bold |
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| State at 25 °C | Solid |
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| Melting point | 3306 K3032.85 °C |
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| Boiling point | 5285 K5011.85 °C |
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| Density | 22.59 g/cm³ |
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Atomic properties
| First ionization energy | 8.438 eV |
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| Electron affinity | 106.1 kJ/mol |
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| Atomic radius | 135 pm |
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| Covalent radius | 144 pm |
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| Van der Waals radius | 216 pm |
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| Common ions | Os⁴⁺ |
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| Protons, neutrons, electrons | 76, 114, 76 |
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Physical and thermal properties
| Molar volume | 8.42 cm³/mol |
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| Heat of fusion | 31 kJ/mol |
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| Heat of vaporization | 630 kJ/mol |
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| Specific heat | 130 J/(kg·K) |
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| Thermal conductivity | 87 W/(m·K) |
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| Thermal expansion | 5.1 × 10⁻⁶ K⁻¹ |
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| Mohs hardness | 7 |
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| Young’s modulus | --- |
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| Crystal structure | Simple hexagonal |
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| Magnetic type | Paramagnetic |
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Identification and history
| CAS number | 7440-04-2 |
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| Latin name | Osmium |
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| Discovered by | Smithson Tennant · 1803 |
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| Named by | --- |
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Natural isotopes
| Isotope | Mass (u) | Abundance |
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| 184Os | 183.952493 | 0.02 % |
| 186Os | 185.953838 | 1.59 % |
| 187Os | 186.95575 | 1.96 % |
| 188Os | 187.955837 | 13.24 % |
| 189Os | 188.958146 | 16.15 % |
| 190Os | 189.958445 | 26.26 % |
| 192Os | 191.961479 | 40.78 % |
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