Frae Wikipedia
Lowp tae: navigation, rake
Selenium,  34Se
General properties
Name, seembol selenium, Se
Appearance black an reid allotropes
Pronunciation /sˈlniəm/ si-LEE-nee-əm
Selenium in the periodic cairt
Hydrogen (diatomic nonmetal)
Helium (noble gas)
Lithium (alkali metal)
Beryllium (alkaline yird metal)
Boron (metalloid)
Carbon (polyatomic nonmetal)
Nitrogen (diatomic nonmetal)
Oxygen (diatomic nonmetal)
Fluorine (diatomic nonmetal)
Neon (noble gas)
Sodium (alkali metal)
Magnesium (alkaline yird metal)
Aluminium (post-transeetion metal)
Silicon (metalloid)
Phosphorus (polyatomic nonmetal)
Sulfur (polyatomic nonmetal)
Chlorine (diatomic nonmetal)
Argon (noble gas)
Potassium (alkali metal)
Calcium (alkaline yird metal)
Scandium (transeetion metal)
Titanium (transeetion metal)
Vanadium (transeetion metal)
Chromium (transeetion metal)
Manganese (transeetion metal)
Airn (transeetion metal)
Cobalt (transeetion metal)
Nickel (transeetion metal)
Capper (transeetion metal)
Zinc (transeetion metal)
Gallium (post-transeetion metal)
Germanium (metalloid)
Arsenic (metalloid)
Selenium (polyatomic nonmetal)
Bromine (diatomic nonmetal)
Krypton (noble gas)
Rubidium (alkali metal)
Strontium (alkaline yird metal)
Yttrium (transeetion metal)
Zirconium (transeetion metal)
Niobium (transeetion metal)
Molybdenum (transeetion metal)
Technetium (transeetion metal)
Ruthenium (transeetion metal)
Rhodium (transeetion metal)
Palladium (transeetion metal)
Siller (transeetion metal)
Cadmium (transeetion metal)
Indium (post-transeetion metal)
Tin (post-transeetion metal)
Antimony (metalloid)
Tellurium (metalloid)
Iodine (diatomic nonmetal)
Xenon (noble gas)
Caesium (alkali metal)
Barium (alkaline yird metal)
Lanthanum (lanthanide)
Cerium (lanthanide)
Praseodymium (lanthanide)
Neodymium (lanthanide)
Promethium (lanthanide)
Samarium (lanthanide)
Europium (lanthanide)
Gadolinium (lanthanide)
Terbium (lanthanide)
Dysprosium (lanthanide)
Holmium (lanthanide)
Erbium (lanthanide)
Thulium (lanthanide)
Ytterbium (lanthanide)
Lutetium (lanthanide)
Hafnium (transeetion metal)
Tantalum (transeetion metal)
Tungsten (transeetion metal)
Rhenium (transeetion metal)
Osmium (transeetion metal)
Iridium (transeetion metal)
Platinum (transeetion metal)
Gold (transeetion metal)
Mercur (transeetion metal)
Thallium (post-transeetion metal)
Leid (post-transeetion metal)
Bismuth (post-transeetion metal)
Polonium (post-transeetion metal)
Astatine (metalloid)
Radon (noble gas)
Francium (alkali metal)
Radium (alkaline yird metal)
Actinium (actinide)
Thorium (actinide)
Protactinium (actinide)
Uranium (actinide)
Neptunium (actinide)
Plutonium (actinide)
Americium (actinide)
Curium (actinide)
Berkelium (actinide)
Californium (actinide)
Einsteinium (actinide)
Fermium (actinide)
Mendelevium (actinide)
Nobelium (actinide)
Lawrencium (actinide)
Rutherfordium (transeetion metal)
Dubnium (transeetion metal)
Seaborgium (transeetion metal)
Bohrium (transeetion metal)
Hassium (transeetion metal)
Meitnerium (unkent chemical properties)
Darmstadtium (unkent chemical properties)
Roentgenium (unkent chemical properties)
Copernicium (transeetion metal)
Ununtrium (unkent chemical properties)
Flerovium (post-transeetion metal)
Ununpentium (unkent chemical properties)
Livermorium (unkent chemical properties)
Ununseptium (unkent chemical properties)
Ununoctium (unkent chemical properties)


Atomic nummer (Z) 34
Group, block group 16 (chalcogens), p-block
Period period 4
Element category   polyatomic nonmetal, sometimes considered a metalloid
Staundart atomic wicht (±) (Ar) 78.971(8)
Electron configuration [Ar] 3d10 4s2 4p4
per shell
2, 8, 18, 6
Pheesical properties
Phase solid
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
Creestal structur hexagonal
Hexagonal crystal 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
Diskivery Jöns Jakob Berzelius an Johann Gottlieb Gahn (1817)
First isolation Jöns Jakob Berzelius an Johann Gottlieb Gahn (1817)
Maist stable isotopes o selenium
iso NA hauf-life DM DE (MeV) DP
72Se syn 8.4 d ε - 72As
γ 0.046 -
74Se 0.87% - (β+β+) 1.2094 74Ge
75Se syn 119.779 d ε - 75As
γ 0.264, 0.136,
76Se 9.36% 76Se is stable wi 42 neutrons
77Se 7.63% 77Se is stable wi 43 neutrons
78Se 23.78% 78Se is stable wi 44 neutrons
79Se trace 3.27×105 y β 0.151 79Br
80Se 49.61% - (ββ) 0.1339 80Kr
82Se 8.73% 1.08×1020 y ββ 2.995 82Kr
Decay modes in parentheses are predictit, but hae nae yet been observed
· references

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.