Revision as of 02:26, 18 February 2021 by imported>Double sharp
[[Category:Template:Pagetype with short description]]
Selenium, 34Se| File:SeBlackRed.jpg |
| Selenium |
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| Pronunciation | (Template:Respell) |
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| Appearance | grey metallic-looking, red, and vitreous black (not pictured) allotropes |
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| Standard atomic weight Ar, std(Se) | Template:Val[1] |
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| Selenium in the periodic table |
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|
|
| Atomic number (Z) | 34 |
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| Group | group 16 (chalcogens) |
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| Period | period 4 |
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| Block | p-block |
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| Electron configuration | [Ar] 3d10 4s2 4p4 |
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| Electrons per shell | 2, 8, 18, 6 |
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| Physical properties |
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| Phase at STP | solid |
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| Melting point | 494 K (221 °C, 430 °F) |
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| Boiling point | 958 K (685 °C, 1265 °F) |
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| Density (near r.t.) | gray: 4.81 g/cm3 alpha: 4.39 g/cm3 vitreous: 4.28 g/cm3 |
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| when liquid (at m.p.) | 3.99 g/cm3 |
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| Critical point | 1766 K, 27.2 MPa |
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| Heat of fusion | gray: 6.69 kJ/mol |
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| Heat of vaporization | 95.48 kJ/mol |
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| Molar heat capacity | 25.363 J/(mol·K) |
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Vapor pressure
| P (Pa)
|
1
|
10
|
100
|
1 k
|
10 k
|
100 k
|
| at T (K)
|
500
|
552
|
617
|
704
|
813
|
958
|
|
| Atomic properties |
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| Oxidation states | −2, −1, +1,[2] +2, +3, +4, +5, +6 (a strongly acidic oxide) |
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| Electronegativity | Pauling scale: 2.55 |
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| Ionization energies | - 1st: 941.0 kJ/mol
- 2nd: 2045 kJ/mol
- 3rd: 2973.7 kJ/mol
-
|
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| Atomic radius | empirical: 120 pm |
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| Covalent radius | 120±4 pm |
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| Van der Waals radius | 190 pm |
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| Spectral lines of selenium |
| Other properties |
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| Natural occurrence | primordial |
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| Crystal structure | hexagonal |
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| Speed of sound thin rod | 3350 m/s (at 20 °C) |
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| Thermal expansion | amorphous: 37 µm/(m·K) (at 25 °C) |
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| Thermal conductivity | amorphous: 0.519 W/(m·K) |
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| Magnetic ordering | diamagnetic[3] |
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| Magnetic susceptibility | −25.0·10−6 cm3/mol (298 K)[4] |
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| Young's modulus | 10 GPa |
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| Shear modulus | 3.7 GPa |
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| Bulk modulus | 8.3 GPa |
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| Poisson ratio | 0.33 |
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| Mohs hardness | 2.0 |
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| Brinell hardness | 736 MPa |
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| CAS Number | 7782-49-2 |
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| History |
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| Naming | after Selene, Greek goddess of the moon |
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| Discovery and first isolation | Jöns Jakob Berzelius and Johann Gottlieb Gahn (1817) |
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| Main isotopes of selenium |
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|
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16x16px Category: Selenium | references |
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References
These references will appear in the article, but this list appears only on this page.
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