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Atomic: M.A.C. | Reference
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Reactions of Selenium
Reactions with air
Selenium burns in air to form the selenium(IV) oxide.
  Se8(s) + 8O2(g)8SeO2(s)
Reactions with halogens
Selenium reacts with fluorine and burns to form the selenium(VI) fluoride.
  Se8(s) + 24F2(g)8SeF6(l)
Selenium (preferably suspended in CS2) reacts with chlorine and bromine to form diselenium dichloride and diselenium dibromide, respectively.
  Se8(s) + 4Cl2(g)4Se2Cl2(l)
  Se8(s) + 4Br2(l)4Se2Br2(l)
When carefully done, selenium reacts with fluorine at 0°C to form the selenium(IV) fluoride. Selenium also reacts under controlled conditions with the other halogens chlorine, bromine, and iodine, to form selenium(IV) tetrahalides.
  Se8(s) + 16F2(g)8SeF4(s)
  Se8(s) + 16Cl2(g)8SeCl4(s)
  Se8(s) + 16Br2(g)8SeBr4(s)
  Se8(s) + 16I2(g)8SeI4(s)
Reactions with acids
Selenium does not react with dilute non-oxidizing acids.
 
Reduction Potentials
Balanced half-reaction E0 / V
SeO42- + 2H+ + 2e-SeO32- + H2O +0.880
SeO42- + H2O + 2e-SeO32- + 2OH- +0.05
SeO42- + 3H+ + 2e-HSeO3- + H2O +1.075
SeO42- + 4H+ + 2e-H2SeO3 + H2O +1.15
HSeO4- + 3H+ + 2e-H2SeO3 + H2O +1.090
SeO32- + 6H+ + 4e-Se(s) + 3H2O +0.875
HSeO3- + 5H+ + 4e-Se(s) + 3H2O +0.778
H2SeO3 + 4H+ + 4e-Se(s) + 3H2O +0.740
SeO32- + 6H+ + 6e-Se2- + 3H2O +0.276
SeO32- + 7H+ + 6e-HSe- + 3H2O +0.414
HSeO3- + 6H+ + 6e-HSe- + 3H2O +0.349
HSeO3- + 7H+ + 6e-H2Se(g) + 3H2O +0.386
H2SeO3 + 6H+ + 6e-H2Se(g) + 3H2O +0.360
Se(s) + 2H+ + 2e-H2Se(g) -0.369
Se(s) + 2e-Se2- -0.924
Se(s) + H+ + 2e-HSe- -0.510
Se(s) + 2H+ + 2e-H2Se(g) -0.399