ATOMIC & NUCLEAR PHYSICS INORGANIC CHEMISTRY A  B  C  D  E  F  G  H  I  J  K  L  M  N  O  P  Q  R  S  T  U  V  W  X  Y  Z                    HOME ABOUT CATEGORIES SITE MAP COPYRIGHT ADVERTISE CONTACT entire Web this site neptunium (Np) 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 is produced synthetically by nuclear reactions. Neptunium was first synthesized in 1940 and is obtained as a by-product in nuclear reactors. 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) Related categories    • ATOMIC AND NUCLEAR PHYSICS    • INORGANIC CHEMISTRY Also on this site: Encyclopedia of Alternative Energy & Sustainable Living Encyclopedia of History Transport Concepts & Designs (partner site) BACK TO TOP