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neptunium |
3 definitions found From Webster's Revised Unabridged Dictionary (1913) [web1913]: Neptunium \Nep*tu"ni*um\, n. [NL.] A new metallic element, of doubtful genuineness and uncertain indentification, said to exist in certain minerals, as columbite. From WordNet r 1.6 [wn]: neptunium n : a radioactive transuranic metallic element; found in trace amounts in uranium ores; a by-product of the production of plutonium [syn: {Np}, {atomic number 93}] From Elements database 20001107 [elements]: 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 isotopes have mass numbers 229 through 236, and 238 through 241. Np-236 has a half-life of 5*10^3 years. First produced by Edwin M. McMillan and P.H. Abelson in 1940.
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