7439-99-8 Usage
Uses
Used in Nuclear Research:
Neptunium is used as a source material for the production of 238U, which serves as a power source in various applications. Its radioactive properties make it valuable for research and development in the field of nuclear energy.
Used in Neutron Detection Instruments:
Neptunium-237 is utilized in instruments designed to detect neutrons due to its radioactive decay properties. This isotope decays through alpha decay into protactinium-233, making it a suitable material for neutron detection applications.
Isotopes
There are a total of 23 isotopes of neptunium. None are stable. All are radioactivewith half-lives ranging from two microseconds to 2.144×10+6years for the isotopeNp-237, which spontaneously fissions through alpha decay.
Origin of Name
Named for the planet Neptune.
Characteristics
Neptunium is the first of the subseries of the actinide series known as the transuranic elements—those heavy, synthetic (man-made) radioactive elements that have an atomic numbergreater than uranium in the actinide series of the periodic table. An interesting fact is thatneptunium was artificially synthesized before small traces of it were discovered in nature. Moreis produced by scientists every year than exists in nature.Neptunium has an affinity for combining with nonmetals (as do all transuranic elements)such as oxygen, the halogens, sulfur, and carbon.
History
Neptunium
was the first synthetic transuranium element of the actinide
series discovered; the isotope 239Np was produced by McMillan
and Abelson in 1940 at Berkeley, California, as the result of
bombarding uranium with cyclotron-produced neutrons. The
isotope 237Np (half-life of 2.14 × 106 years) is currently obtained
in gram quantities as a by-product from nuclear reactors in
the production of plutonium. Twenty-three isotopes and isomers
of neptunium are now recognized. Trace quantities of
the element are actually found in nature due to transmutation
reactions in uranium ores produced by the neutrons which are
present. Neptunium is prepared by the reduction of NpF3 with
barium or lithium vapor at about 1200°C. Neptunium metal
has a silvery appearance, is chemically reactive, and exists in
at least three structural modifications: α-neptunium, orthorhombic,
density 20.25 g/cm3, β-neptunium (above 280°C),
tetragonal, density (313°C) 19.36 g/cm3; γ-neptunium (above
577°C), cubic, density (600°C) 18.0 g/cm3. Neptunium has four
ionic oxidation states in solution: Np+3 (pale purple), analogous
to the rare earth ion Pm+3, Np+4 (yellow green); NpO+ (green
blue); and NpO++ (pale pink). These latter oxygenated species
are in contrast to the rare earths that exhibit only simple ions
of the (II), (III), and (IV) oxidation states in aqueous solution.
The element forms triand tetrahalides such as NpF3, NpF4,
NpCl4, NpBr3, NpI3, and oxides of various compositions such
as are found in the uranium-oxygen system, including Np3O88
and NpO2.
Production Methods
Neptunium-237 is obtained as a by-product of making plutonium from uranium isotopes in nuclear reactors. Significant amounts of this element may be recovered from plutonium plant nuclear wastes. Both the recovery and purification of neptunium can be carried out by various chemical processes, including precipitation, solvent extraction and ion exchange.
Neptunium-237 may be synthesized by bombarding uranium-235 or uranium-238 with neutrons:
Neptunium-239 may be obtained from uranium-238 by neutron bombardment as it was first produced:
Neptunium may be prepared in the metallic state by the reduction of its trifluoride with barium vapor at 1,200°C followed by rapid cooling. Its tetrafluoride may be reduced with excess calcium metal at about 750°C under argon atmosphere.
Hazard
A radioactive poison.
Hazard
All isotopes of neptunium are highly radioactive and are hazardous and thus need to becarefully used in controlled laboratory settings. These isotopes as well as neptunium’s compoundsare radioactive poisons.
References
Turlington et al. (2012) Non-covalent triazole-based inhibitors of the SARS main protease 3CLpro; In: Probe Reports from the NIH Molecular Libraries Program
Turlington et al. (2013) Discovery of N-(Benzo[1,2,3]triazol-1-yl)-N-(benzyl)acetamido)phenyl)carboxamides as severe acute respiratory syndrome coronavirus (SARS-CoV) 3CLpro inhibitors: Identification of ML300 and noncovalent nanomolar inhibitors with an induced-fit binding; Bioorg. Med. Chem. Lett. 23 6172
Check Digit Verification of cas no
The CAS Registry Mumber 7439-99-8 includes 7 digits separated into 3 groups by hyphens. The first part of the number,starting from the left, has 4 digits, 7,4,3 and 9 respectively; the second part has 2 digits, 9 and 9 respectively.
Calculate Digit Verification of CAS Registry Number 7439-99:
(6*7)+(5*4)+(4*3)+(3*9)+(2*9)+(1*9)=128
128 % 10 = 8
So 7439-99-8 is a valid CAS Registry Number.
InChI:InChI=1/Np
