neptunium

nep·tu·ni·um   (něp-tōō'nē-əm, -tyōō'-)    n.   Symbol Np A silvery, metallic, naturally radioactive element, atomic number 93, the first of the transuranium elements. Its longest-lived isotope is Np-237 with a half-life of 2.1 million years. Found in trace quantities in uranium ores, it is produced synthetically by nuclear reactions. See Table at element. [After the planet Neptune (from the fact that it follows uranium in the periodic table).]

Main Entry: nep·tu·ni·um
Pronunciation: nep-'t(y)ü-nE-&m
Function: noun
: a radioactive metallic element that is chemicallysimilar to uranium and is obtained in nuclear reactors as a by-product in the production of plutonium —symbol Np; —see ELEMENT table
Nepátune /'nep-"t(y)ün/, Roman mythological character. Neptune was originally the god of fresh water. Later he became identified with theGreek god Poseidon, a deity of the sea. In art Neptune is usually represented as a bearded man holding a trident and sometimes a fish. The planet Neptune was named after him and the element neptuniumwas named after the planet.

neptunium nep·tu·ni·um (něp-t&oomacr;'nē-əm, -ty&oomacr;'-)
n.
Symbol Np
A metallic radioactive element found in trace quantities in uranium ores or synthesized; its longest-lived isotope is Np 237 with a half-life of 2.1 million years. Atomic number 93.

neptunium   (něp-t'nē-əm)  Pronunciation Key  Symbol Np A silvery, radioactive metallic element of the actinide series. It occurs naturally in minute amounts in uranium ores and is produced artificially as a byproduct of plutonium production. Its longest-lived isotope is Np 237 with a half-life of 2.1 million years. Atomic number 93. See Periodic Table.

neptunium

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 and Philip H. Abelson 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.

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