Selenium

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Selenium,  34Se
SeBlackRed.jpg
General properties
Appearance black an reid allotropes
Staundart atomic wecht (Ar, staundart) 78.971(8)
Selenium in the periodic cairt
Hydrogen Helium
Lithium Beryllium Boron Carbon Nitrogen Oxygen Fluorine Neon
Sodium Magnesium Aluminium Silicon Phosphorus Sulfur Chlorine Argon
Potassium Calcium Scandium Titanium Vanadium Chromium Manganese Airn Cobalt Nickel Capper Zinc Gallium Germanium Arsenic Selenium Bromine Krypton
Rubidium Strontium Yttrium Zirconium Niobium Molybdenum Technetium Ruthenium Rhodium Palladium Siller (element) Cadmium Indium Tin Antimony Tellurium Iodine Xenon
Caesium Barium Lanthanum Cerium Praseodymium Neodymium Promethium Samarium Europium Gadolinium Terbium Dysprosium Holmium Erbium Thulium Ytterbium Lutetium Hafnium Tantalum Tungsten Rhenium Osmium Iridium Platinum Gold Mercur (element) Thallium Leid (element) Bismuth Polonium Astatine Radon
Francium Radium Actinium Thorium Protactinium Uranium Neptunium Plutonium Americium Curium Berkelium Californium Einsteinium Fermium Mendelevium Nobelium Lawrencium Rutherfordium Dubnium Seaborgium Bohrium Hassium Meitnerium Darmstadtium Roentgenium Copernicium Ununtrium Flerovium Ununpentium Livermorium Ununseptium Ununoctium
S

Se

Te
arsenicseleniumbromine
Atomic nummer (Z) 34
Group group 16 (chalcogens)
Period period 4
Element category   polyatomic nonmetal
Block p-block
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 6, 4, 2, 1,[1] -2
(strangly acidic oxide)
Electronegativity Pauling scale: 2.55
Atomic radius empirical: 120 pm
Covalent radius 120±4 pm
Van der Waals radius 190 pm
Color lines in a spectral range
Miscellanea
Creestal structurhexagonal
Hexagonal creestal structur for selenium
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[2]
Young's modulus 10 GPa
Shear modulus 3.7 GPa
Bouk 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
Iso­tope Abun­dance Hauf-life (t1/2) Decay mode Pro­duct
72Se syn 8.4 d ε 72As
γ -
74Se 0.87% - (β+β+) 74Ge
75Se syn 119.779 d ε 75As
γ -
76Se 9.36% stable
77Se 7.63% stable
78Se 23.78% stable
79Se trace 3.27×105 y β 79Br
80Se 49.61% - (ββ) 80Kr
82Se 8.73% 1.08×1020 y ββ 82Kr
Decay modes in parentheses are predictit, but hae nae yet been observed
| references | in Wikidata

Selenium is a chemical element wi seembol Se an atomic nummer 34. It is a nonmetal wi properties that are intermediate atween those o its periodic cairt column-adjacent chalcogen elements sulphur an tellurium. It rarely occurs in its elemental state in naitur, or as pure ore compoonds. Selenium (Greek σελήνη selene meanin "Muin") wis discovered in 1817 bi Jöns Jacob Berzelius, who notit the seemilarity o the new element tae the previously kent tellurium (named for the Yird).

References[eedit | eedit soorce]

  1. Greenwood, Norman N.; Earnshaw, Alan (1997). Chemistry of the Elements (2nd ed.). Butterworth–Heinemann. ISBN 0080379419. 
  2. 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.