Neptunium
neptunium · neptunium atom · neptunium USP/EP/BP
Identifikatoren & physikalische Daten
| CAS No. | 22537-61-7 |
|---|---|
| Summenformel | Np |
| Durchschnittliche Molmasse | 237,0482 g/mol |
| Monoisotopische Masse | 237,04817 g/mol |
| SMILES | [Np] |
| InChIKey | LFNLGNPSGWYGGD-UHFFFAOYSA-N |
| PubChem CID | 23933 |
| ChEBI | CHEBI:33387 |
| EC No. | 231-108-8 |
| DTXSID | DTXSID5074840 |
| Lokaler Name | Neptunium |
Chemische & physikalische Eigenschaften
| Polarare Oberfläche (TPSA) | 0 |
|---|---|
| H-Brücken-Donoren | 0 |
| H-Brücken-Akzeptoren | 0 |
| Frei drehbare Bindungen | 0 |
| Schwere Atome | 1 |
| Formalladung | 0 |
| Komplexität | 0 |
| Stoffklassen | Physical/Radiation -> Radionuclides |
| SpringerMaterials Properties | electron density of states |
| Physical Description | A man-made, radioactive metal with a melting point of 577 degrees C[Merck Index # 6471] |
| Schmelzpunkt | 637° |
| Siedepunkt | bp 4174° |
| Dichte | 20.45d 19.36 |
| Lagerbedingungen | -20°C |
| Löslichkeit | Soluble in DMSO (>25 mg/ml)soluble HCl [HAW93] |
| Aggregatzustand | silvery metal |
| Farbe | Off-white |
| Stabilität | Stable for 1 year from date of purchase as supplied. Solutions in DMSO may be stored at -20°C for up to 1 month. |
| Shear Modulus | 80.0 GPa |
| Hardness, Vickers | 346 |
| Bulk Modulus | 118 GPa |
| CAS Datenbank | 7439-99-8 |
| EPA chemische Informationen | Neptunium (7439-99-8) |
Sicherheit & Vorschriften
| Gefahrenübersicht | Neptunium is toxic after ingestion or inhalation. Some of the isotopes also have a small risk of generating significant external radiation (Np-236 and Np-237). [Argonne] Most Important Radionuclide: Np-237 Half-Life: 2.1 million years Effective Half-Life: 200 years Specific Activity: 0.00071 Ci/g Decay Mode: Alpha GI Absorption: 0.05% Lung Clearance Half-Time: Weeks (10-100 days) for all compoundsCritical Organ: Bone Internal Toxicity: Very High Annual Limit on Intake: 0.000004 mCi Average Radiation Energy (MeV): Alpha 4.8Beta 0.070Gamma 0.035 [Argonne] [See Glossary for references.] See Radiation, ionizing. |
|---|
Anwendungen & Verwendung
Occurrence
At one time, neptunium’s entire existence was synthesized by man. Sometime later, in themid-twentieth century, it was discovered that a very small amount is naturally produced inuranium ore through the actions of neutrons produced by the decay of uranium in the orepitchblende. Even so, a great deal more neptunium is artificially produced every year than everdid or does exist in nature. Neptunium is recovered as a by-product of the commercial productionof plutonium in nuclear reactors. It can also be synthesized by bombarding uranium-238with neutrons, resulting in the production of neptunium-239, an isotope of neptunium witha half-life of 2.3565 days.
History
Neptunium was first discovered in 1940 by Edwin Mattison McMillan and Philip Abelson during their research on nuclear fission. It is a decay product of uranium. When a uranium target is bombarded with slow neutrons, the target subsequently emits unusual beta rays, indicating the presence of a new isotope, thus generating its most famous isotope—neptunium-239.
Verwenden
The most important radioactive isotope of neptunium is Neptunium-237, with a half-lifeof 2.144×10+6years, or about 2.1 million years, and decays into protactinium-233 throughalpha decay. Neptunium’s most important use is in nuclear research and for instrumentsdesigned to detect neutrons.