Selenium
Physico-chemical properties
DACTARI
Element
Symbol
Atomic number
Atomic weight
Chemical series
Discovered
Origin of the name
Electron configuration
Density
Melting point
Boiling point
Pearson classification (acid and base)
Electronegativity (Pauling scale)
Ionic Radius (Marcus)
Coordination number
Oxidation states (main in bold)
Redox potential
Main mineral compounds (solids)
Main inorganic compounds
Main organic compounds
Main industrial compounds (solution)
Biological role
Main isotopes
Selenium
Se
34
78.96
nonmetals
J.J. Berzelius (1817)
Greek selene meaning "moon"
[Ar] 3d10 4s2 4p4
4.8 g/cm3
221°C
685°C
Border
2.55
-II (SeH2) 1.98 Å; VI (SeO42-) 0.42 Å
4-6
-II (SeH2), 0 (Se), IV (SeO32-), VI (SeO42-)
+ 0.74 (Se4+/Se), +1.15 (Se6+/Se4+),
HgSe, H2Se, SeO2, Se4S4, SeS2, Se2S6, Na2SeO3,
ZnSe…
Dimethyl selenide : selenocysteine, selenomethionine
Selenites (SeO32-), Selenates (SeO42-)
Present in enzymes (selenocysteins) and plays a role
in thyroid (thyroid hormone deiodinases)
75Se (T1/2 = 119 .8 d, EC, ) (1g = 5.0 1014 Bq)
79Se (T1/2 = 1.1 106 y, β) (1g = 1.52 108 Bq)
Selenium
Selenium acute toxicity
DACTARI
Element
Symbol
Selenium metal
Natrium selenite : Na2SeO3
Natrium selenate : Na2SeO4
Selenium sulfide, disulfide : SeS, SeS2
Selenium dioxide : SeO2
L-selenocystine
Selenium
Se
LD 50 (mg/kg) (rat/oral)
Classification LD50*
6700
NC
7
2
1.6
1
38 - 138
2-3
48
2
36 (mice)
2
References
Fractional absorption : fA (ICRP 100)
Materno-fœtal transfer (ICRP 88)
HSDB, INRS (FT 150), OEHHA (2010)
0.8
2
*Classification of Acute Toxicity on the Basis of the LD 50.
Exposure Route
Oral (mg/kg
bodyweight)
Dermal (mg/kg
bodyweight)
Gases (ppmV)
Vapours (mg/l)
Category 1
Category 2
Category 3
Category 4
ATE < 5
5 < ATE < 50
50 < ATE < 300
300 < ATE < 2000
ATE ≤ 50
50 < ATE < 200
200 < ATE < 1000
1000 < ATE < 2000
ATE < 100
100 < ATE < 500
500 < ATE < 2500
2500 < ATE < 20000
ATE < 0.5
0.5 < ATE < 2.0
2.0 < ATE < 10.0
10.0 < ATE < 20.0
*Acute toxicity hazard categories and acute toxicity estimates (ATE)
* Classification du GHS (United Nations Globally Harmonised System of Classification and Labelling of
Chemicals) des DL50 devant rentrer en vigueur en Europe en 2008. Proposal for a regulation of the
European parliament and of the council on classification, labelling and packaging of substances and
mixtures, and amending Directive 67/548/EEC and Regulation (EC) No 1907/2006.
Commission of the European Communities, Brussels, 27.6.2007 - COM(2007) 355 final , 2007/0121
(COD).Volume II (Annex I),
http://ec.europa.eu/enterprise/reach/ghs_legislation_en.htm (volume 2, annexe 1 )
Selenium
Chronic toxicity
DACTARI
Element
Symbol
Isotopes
75Se
WHO
RN water guide value (Bq/L)
chemical water guide value (mg/L)
CMR classification
IARC (1 to 4)
CEE
EPA
Non carcinogen
Critical effect
RfD (reference dose) mg/kg/d
NOAEL
79Se
100
0.01
Selenium compounds C:3
-
-
Target organs : Liver, kidneys
5 10-3 (EPA)
Selenite 0.2 mg/kg/d (food)
Selenite 0.4 mg/kg/d (water)
Selenate 0.4 mg/kg/d (food)
R 23-25-33
Risk phrases
Risk group (Delacroix)
3
# Specific activities : 75Se (1g = 5.0 1014 Bq) ; 79Se (1g = 5.7 108 Bq)
IARC carcinogenicity to humans:
C:1
C : 2A
C : 2B
C:3
C:4
Carcinogenic to humans
Probably carcinogenic to humans
Possibly carcinogenic to humans
Unclassifiable as to carcinogenicity for humans
Probably not carcinogenic for humans
Radiotoxic groups (Delacroix et al., 2002) :
G 1 : Exemption < 104 Bq
G 2 : Exemption < 105 Bq
G 3 : Exemption = 106 Bq
G 4 : Exemption = 107 Bq
G 5 : Exemption > 108 Bq
Selenium
Se
Chemical compound