Selenium, 34Se |
| Selenium |
|---|
| Pronunciation | (sih-LEE-nee-əm) |
|---|
| Appearance | black an reid allotropes |
|---|
| Standard atomic weight Ar, std(Se) | 7001789710000000000♠78.971(8)[1] |
|---|
| Selenium in the periodic cairt |
|---|
|
|
| Atomic nummer (Z) | 34 |
|---|
| Group | group 16 (chalcogens) |
|---|
| Period | period 4 |
|---|
| Block | p-block |
|---|
| Element category | Reactive nonmetal |
|---|
| Electron confeeguration | [Ar] 3d10 4s2 4p4 |
|---|
| Electrons per shell | 2, 8, 18, 6 |
|---|
| Pheesical properties |
|---|
| Phase at STP | solit |
|---|
| Meltin pynt | 494 K (221 °C, 430 °F) |
|---|
| Bylin pynt | 958 K (685 °C, 1265 °F) |
|---|
| Density (near r.t.) | (gray) 4.81 g/cm3
(alpha) 4.39 g/cm3
(vitreous) 4.28 g/cm3 |
|---|
| when liquid (at m.p.) | 3.99 g/cm3 |
|---|
| Creetical pynt | 1766 K, 27.2 MPa |
|---|
| Heat o fusion | (gray) 6.69 kJ/mol |
|---|
| Heat o vapourisation | 95.48 kJ/mol |
|---|
| Molar heat capacity | 25.363 J/(mol·K) |
|---|
Vapour pressur
| P (Pa)
|
1
|
10
|
100
|
1 k
|
10 k
|
100 k
|
| at T (K)
|
500
|
552
|
617
|
704
|
813
|
958
|
|
| Atomic properties |
|---|
| Oxidation states | −2, −1, +1,[2] +2, +3, +4, +5, +6 strangly acidic |
|---|
| Electronegativity | Pauling scale: 2.55 |
|---|
| Atomic radius | empirical: 120 pm |
|---|
| Covalent radius | 120±4 pm |
|---|
| Van der Waals radius | 190 pm |
|---|
 Colour lines in a spectral rangeSpectral lines o selenium |
| Ither properties |
|---|
| Naitural occurrence | primordial |
|---|
| Creestal structur | hexagonal |
|---|
| Speed o soond thin rod | 3350 m/s (at 20 °C) |
|---|
| Thermal expansion | (amorphous) 37 µm/(m·K) (at 25 °C) |
|---|
| Thermal conductivity | (amorphous) 0.519 W/(m·K) |
|---|
| Magnetic orderin | diamagnetic[3] |
|---|
| Young's modulus | 10 GPa |
|---|
| Shear modulus | 3.7 GPa |
|---|
| Bulk modulus | 8.3 GPa |
|---|
| Poisson ratio | 0.33 |
|---|
| Mohs haurdness | 2.0 |
|---|
| Brinell haurdness | 736 MPa |
|---|
| CAS Nummer | 7782-49-2 |
|---|
| History |
|---|
| Diskivery | Jöns Jakob Berzelius an Johann Gottlieb Gahn (1817) |
|---|
| First isolation | Jöns Jakob Berzelius an Johann Gottlieb Gahn (1817) |
|---|
| Main isotopes o selenium |
|---|
|
|
| Decay modes in parentheses are predictit, but hae nae yet been observed |
| | references |
| style="text-align:left"|
|
|
|
in
|
calc from C
|
diff
|
report
|
ref
|
| C
|
221
|
—
|
—
|
|
|
| K
|
494
|
494
|
0
|
|
|
| F
|
430
|
430
|
0
|
|
|
| WD
|
392 !392 Fahrenheit 
|
|
|
[5]
|
| input
|
C: 221, K: 494, F: 430
|
| comment
|
|
| style="text-align:left"|
|
|
|
in
|
calc from C
|
diff
|
report
|
ref
|
| C
|
685
|
—
|
—
|
|
|
| K
|
958
|
958
|
0
|
|
|
| F
|
1265
|
1265
|
0
|
|
|
| WD
|
1265 !1265 Fahrenheit
|
|
|
[5]
|
| input
|
C: 685, K: 958, F: 1265
|
| comment
|
|
References
Thir references will appear in the airticle, but this list appears anerly on this page.
- ↑ Meija, Juris; et al. (2016). "Atomic weights of the elements 2013 (IUPAC Technical Report)". Pure and Applied Chemistry. 88 (3): 265–91. doi:10.1515/pac-2015-0305.
- ↑ Greenwood, Norman N.; Earnshaw, Alan (1997). Chemistry of the Elements (2nd ed.). Butterworth–Heinemann. ISBN 0080379419.
- ↑ Magnetic susceptibility of the elements and inorganic compounds, in Lide, D. R., ed. (2005). CRC Handbook of Chemistry and Physics (86th ed.). Boca Raton (FL): CRC Press. ISBN 0-8493-0486-5.
- ↑ Greenwood, Norman N.; Earnshaw, Alan (1997). Chemistry of the Elements (2nd ed.). Butterworth–Heinemann. ISBN 0080379419.
- ↑ a b http://www.cdc.gov/niosh/npg/npgd0550.html.
