neptunium
Noun
Meaning
A new metallic element, of doubtful genuineness and uncertain indentification, said to exist in certain minerals, as columbite.
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All of the elements with higher atomic numbers have been first discovered in the laboratory, with neptunium and plutonium later also discovered in nature.
As the first isotope of neptunium to be discovered has such a short half-life, McMillan and Abelson were unable to prepare a sample that was large enough to perform chemical analysis of the new element using the technology that was then available.
Due to its long half-life, neptunium will become the major contributor of the total radiotoxicity in 10,000 years.
Finely divided neptunium metal presents a fire hazard because neptunium is pyrophoric ; small grains will ignite spontaneously in air at room temperature.
For a long time, chemists thought that element 93 would be homologous to rhenium, making the discovery and identification of neptunium nearly impossible.
However, as neptunium does in fact occur in nature in trace amounts, as demonstrated when it was found in uranium ore in 1952, it is possible that Hulubei and Cauchois did in fact observe neptunium.