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Name: Selenium Symbol: Se
Group: Non-Metal, Chalcogen Atomic weight: 78.96
Density @ 293 K: 4.79 g/cm3 Atomic volume: 16.45 cm3/mol
Group: Non-Metal, Chalcogen discovered: 1818


state (s, l, g): s
melting point: 490.2 K boiling point: 958 K
Heat of fusion: 6.694 kJ/mol Heat of vaporization: 37.70 kJ/mol


1st ionization energy: 940.9 kJ/mole
electronegativity: 2.55 2nd ionization energy: 2044.5 kJ/mole
electron affinity: 194.97 kJ/mole 3rd ionization energy: 2973.7 kJ/mole
Specific heat: 0.32 J/gK heat atomization: 227 kJ/mole atoms

Oxidation & Electrons:

Shells: 2,8,18,6 electron configuration: [Ar] 3d10 4s2 4p4
minimum oxidation number: -2 maximum oxidation number: 6
min. common oxidation no.: -2 max. common oxidation no.: 6

Appearance & Characteristics:

structure: parallel chains color: black
uses: Xerography, medicines toxicity: yes
hardness: 2 mohs characteristics: 6 forms


reaction with air: vigorous, w/ht =>SeO2
reaction with 6M HCl: none reaction with 6M HCl: none
reaction with 15M HNO3: mild, =>H2SeO3, NOx reaction with 6M NaOH:

Other Forms:

number of isotopes: 6 hydride(s): SeH2
oxide(s): SeO2 SeO3 chloride(s): Se2Cl2 Se4Cl16


ionic radius (2- ion): 184 pm ionic radius (1- ion): pm
atomic radius: 119 pm ionic radius (1+ ion): pm
ionic radius (2+ ion): pm ionic radius (3+ ion): pm


thermal conductivity: 0.52 J/m-sec-deg
electrical conductivity: 0 1/mohm-cm polarizability: 3.8 A^3


source: Cu smelting by-product
rel. abund. solar system: 1.793 log abundance earth's crust: -1.3 log
cost, pure: 14 $/100g cost, bulk: $/100g