Chemicool

Se

34

78.96
Selenium
General | States | Energies | Oxidation & Electrons |Appearance & Characteristics
Reactions | Other Forms |Radius | Conductivity | Abundance
Encyclopedia Britannica articles

General
Name Selenium Symbol Se
atomic number 34 Atomic weight 78.96
Density @ 293 K 4.79 g/cm3 Atomic volume 16.45 cm3/mol
Group Non-Metal, Chalcogen discovered 1818

States
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
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Energies
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
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Appearance & Characteristics
structure parallel chains color black
uses Xerography, medicines toxicity yes
hardness 2 mohs characteristics 6 forms

Reactions
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
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Other Forms
number of isotopes 6 hydride(s) SeH2
oxide(s) SeO2 SeO3 chloride(s) Se2Cl2 Se4Cl16

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

Abundance
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
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