neptunium

/nep tooh"nee euhm, -tyooh"-/, n. Chem., Physics.
a transuranic element produced in nuclear reactors by the neutron bombardment of U-238: decays rapidly to plutonium and then to U-235. Symbol: Np; at. no.: 93.
[1940-45; NEPTUNE + -IUM]

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 (Np),  
 radioactive chemical element of the actinoid series of the periodic table, first transuranium element to be artificially produced, atomic number 93. Though traces of neptunium have subsequently been found in nature, where it is not primeval but produced by neutron-induced transmutation reactions in uranium ores, Edwin M. McMillan (McMillan, Edwin Mattison) and Philip H. Abelson (Abelson, Philip Hauge) first found neptunium in 1940 after uranium had been bombarded by neutrons from the cyclotron at Berkeley, Calif. Neptunium has been produced in weighable amounts in breeder reactors as a by-product of plutonium production from uranium-238 (about one part neptunium is produced for every 1,000 parts plutonium). All neptunium isotopes are radioactive; the stablest is neptunium-237, with a half-life of 2,140,000 years, and among the most unstable is neptunium-232, with a half-life of 13 minutes.

      Neptunium, a silvery metal, exists in three crystalline modifications; the room-temperature form (alpha) is orthorhombic. Neptunium is chemically reactive and similar to uranium with oxidation states from +3 to +6. Neptunium ions in aqueous solution possess characteristic colours: Np3+, pale purple; Np4+, pale yellow-green; NpO2+, green-blue; NpO22+, varying from colourless to pink or yellow-green, depending on the anion present.

atomic number
93
stablest isotope
237
melting point
640° C (1,184° F)
specific gravity (alpha)
20.45
oxidation states
+3, +4, +5, +6
electronic config.
[Rn]5f46d17s2

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Universalium. 2010.

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  • Neptunium — Nep*tu ni*um, n. [NL.] A radioactive metallic element of atomic number 93, produced in nuclear reactors from Plutonium or Uranium. Symbol Np; The atomic weight of the most stable isotope is 237.0482. [PJC] …   The Collaborative International Dictionary of English

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  • neptunium — Symbol: Np Atomic number: 93 Atomic weight: (237) Radioactive metallic transuranic element, belongs to the actinoids. Np 237, the most stable isotope, has a half life of 2.2*10^6 years and is a by product of nuclear reactors. The other known… …   Elements of periodic system

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  • neptunium — ☆ neptunium [nep to͞o′nē əm, neptyo͞o′nē əm ] n. [ModL < Neptunus, NEPTUNE + IUM: so named by MCMILLAN Edwin MattisonEdwin MattisonEdwin MattisonEdwin MattisonEdwin MattisonEdwin Mattison & P. Abelson (1913 2004), U.S. phys i cists, because… …   English World dictionary

  • Neptunium — uranium ← neptunium → plutonium Pm ↑ Np ↓ (Uqt) …   Wikipedia

  • Neptunium — Eigenschaften …   Deutsch Wikipedia

  • Neptunium — Nep|tu|ni|um 〈n.; s; unz.; chem. 〉 künstliches radioaktives Element, Ordnungszahl 93 [neulat., nach dem Planeten Neptun] * * * Nep|tu|ni|um [nach dem Planeten Neptun, der nach dem Uranus (↑ Uran) entdeckt wurde; ↑ ium (1)], das; s; Symbol: Np: in …   Universal-Lexikon

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