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neptunium (Np)

atom of neptunium
Electron shell structure of neptunium
Source: Wikipedia

A radioactive, silvery, metallic element, atomic number 93. Neptunium is the first of the transuranic elements, having a number of isotopes with mass numbers from 231 to 241 and half-lives ranging from 7.3 minutes to 2.2 million years (the latter in the case of 237Np). It is found in trace quantities in uranium ores and resembles uranium in its chemical properties. is produced synthetically by nuclear reactions. Neptunium was first synthesized in 1940 and is made in breeder reactors as a by-product of plutonium production by neutron irradiation of uranium-238.

atomic number 93
relative atomic mass 237.048
relative density 20.25
melting point 640°C (1,184°F)
boiling point 3,902°C (7,056°F)

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