neptunium Chem.
(nɛpˈtjuːnɪəm)
[mod.L., f. Neptune + -ium.]
† 1. [coined in G. (R. Hermann 1877, in Jrnl. f. prakt. Chem. XV. 105).] A supposed element similar to tantalum found in a sample of tantalite from Haddam, Connecticut, U.S.A. Obs.
| 1877 Jrnl. Chem. Soc. XXXII. 167 Neptunium is distinguished from tantalum by the fact that its fluoride forms an easily soluble double salt with potassium fluoride. 1877 Potter's Amer. Monthly Sept. 238/2 Hermann calls it neptunium. |
2. An artificially produced transuranic element (traces of which have subsequently been found in nature) which is a silvery metal and whose longest-lived isotope has a half-life of about 21/4 million years. Atomic number 93; symbol Np.
The word does not occur in the article by McMillan and Abelson (Physical Rev. (1940) LVII. 1185) in which they announced the discovery of the element, though McMillan is often said to be the coiner (e.g. quot. 1945; cf. also Jrnl. Amer. Chem. Soc. (1948) LXX. 1128 (an abridgement of a secret report of 1942)).
| 1941 Sci. News Let. 30 Aug. 135/1 The uranium outpost was passed some years ago by Prof. Enrico Fermi..with his discovery of the radioactive element No. 93, now called neptunium. 1945 Chem. & Engin. News 10 Dec. 2190/3 Element 93 was given the name neptunium by McMillan after Neptune, the planet immediately beyond Uranus, which gives its name to uranium. 1946 Electronic Engin. XVIII. 88 On bombarding the 238 isotope of uranium with a neutron of resonant energy value, a new isotope of uranium..is formed. This isotope is unstable..and emits one electron to become a new element..called neptunium. 1950 M. Lowry Let. 6 Mar. (1967) 200 Oddly enough I put neptunium in but abandoned it for niobium... I just took the elements out of the dictionary. 1968 New Scientist 23 May 410/2 Neptunium-237 is an important isotope because it is the precursor of plutonium-238. 1974 Encycl. Brit. Micropædia VII. 261/3 Neptunium is chemically reactive and similar to uranium with oxidation states from + 3 to + 6. |