Neptunium
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 Industrial compounds (solids)
Main industrial compounds (solution)
Biological role
Main isotopes
Neptunium
Np
93
237
Actinides
E. McMillan and P.H.Abelson, 1940
Neptune planet
[Rn] 5f4 6d1 7s2
20.2 g/cm3
644°C
4000°C
Hard
1.36
0.95 Å
6-8
4+
III, IV (Np ), V (NpO2+), VI (NpO22+)
0.64 V (Np5+/Np4+)
Not natural
NpO2, NpO, Np2O5, NpF4, NpCl4, Np2S3…
Np(OH)4, Np(HPO4)2, Np(SO4)2…
Not present
237Np (T1/2 = 2.14 106 y, α) (1g = 2.61 107 Bq)
239Np (T1/2 = 2.35 d, β) (1g = 8.60 1015 Bq)
Neptunium
Acute toxicity
DACTARI
Element
Symbol
237Np
Neptunium
Np
LD 50 (mg/kg) (oral, rat)
Classification LD50*
6 – 24 (rat) (iv)*
2
HSDB
5 10-4 – 5 10-3
0.03 - 1
citrate
References
Fractional absorption : fA (ICRP 100)
Materno-fœtal transfer (ICRP 88)
* iv = intravenous injection
# Specific activities: 237Np (1g = 2.61 107 Bq) ; 239Np (1g = 8.60 1015 Bq)
*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 )
Neptunium
Chronic toxicity
DACTARI
Element
Symbol
Isotopes
237Np
Neptunium
Np
Chemical compound
239Np
WHO
RN water guide value (Bq/L)
1
100
chemical water guide value (mg/L)
CMR classification
IARC (1 to 4)
Rn α emitter C : 1
CEE
EPA
Non carcinogen
Critical effect
Target organs : Bone,Liver, kidney
RfD (reference dose) mg/kg/d
NOAEL
Risk phrases
Risk group (Delacroix)
4
# Specific activities : 237Np : 1g = 2.61 107 Bq; 239Np : 1g = 8.60 1015 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