Editing Promethium (section)

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'''Promethium''' is a [[chemical element]]; it has [[Symbol (chemistry)|symbol]] '''Pm''' and [[atomic number]] 61. All of its [[isotope]]s are [[Radioactive decay|radioactive]]; it is extremely rare, with only about 500–600 grams naturally occurring in the Earth's crust at any given time. Promethium is one of the only two radioactive elements that are both preceded and followed in the [[periodic table]] by elements with stable forms, the other being [[technetium]]. Chemically, promethium is a [[lanthanide]]. Promethium shows only one stable [[oxidation state]] of +3.

In 1902 [[Bohuslav Brauner]] suggested that there was a then-unknown element with properties intermediate between those of the known elements [[neodymium]] (60) and [[samarium]] (62); this was confirmed in 1914 by [[Henry Moseley]], who, having measured the atomic numbers of all the elements then known, found that the element with atomic number 61 was missing. In 1926, two groups (one Italian and one American) claimed to have isolated a sample of element 61; both "discoveries" were soon proven to be false. In 1938, during a nuclear experiment conducted at [[Ohio State University]]<!--Wikipedians do not use "The" as part of Ohio State's name; it is considered a marketing gimmick, and routinely deleted.-->, a few radioactive nuclides were produced that certainly were not radioisotopes of neodymium or samarium, but there was a lack of chemical proof that element 61 was produced, and the discovery was not much recognized. Promethium was first produced and characterized at [[Oak Ridge National Laboratory]] in 1945 by the separation and analysis of the fission products of uranium fuel irradiated in a graphite reactor. The discoverers proposed the name "prometheum" (the spelling was subsequently changed), derived from [[Prometheus]], the Titan in Greek mythology who stole fire from Mount Olympus and brought it down to humans, to symbolize "both the daring and the possible misuse of mankind's intellect". A sample of the metal was made only in 1963.

The two sources of natural promethium are rare [[alpha decay]]s of natural [[europium]]-151 (producing promethium-147) and [[spontaneous fission]] of [[uranium]] (various isotopes). Promethium-145 is the most stable promethium isotope, but the only isotope with practical applications is promethium-147, chemical compounds of which are used in [[luminous paint]], [[atomic battery|atomic batteries]] and thickness-measurement devices. Because natural promethium is exceedingly scarce, it is typically synthesized by bombarding uranium-235 ([[enriched uranium]]) with [[thermal neutron]]s to produce promethium-147 as a [[fission product]].