Name       : Neptunium
Symbol     : Nu
Atomic #   : 93
Atom weight: 237
Melting P. : 640
Boiling P. : 3902 (Calculated value)
Oxidation  : +3, +4, +5, +6
Pronounced : nep-TOO-ni-em
From       : Named for the planet Neptune
Identified : Edwin M. McMillan and Philip H. Abelson in 1940
Appearance : Silvery metal
Note       : Produced artificially prior to its discovery in nature
             
[Properties]

  Neptunium is the first of transuranium elements - elements having atomic
numbers higher than that of uranium, number 92. Neptunium belongs to the
actinide series of elements.
  All isotopes of neptunium are radioactive. However, neptunium-237 has a
very long life - on the order of two million years. This long-lived 
isotope was the first to be created in measurable amounts and is the one
that is commercially available today.
  The discovery of neptunium was also important because it provided a
missing link fro a systematic group of radioactive decay processes. It was
known that the thorium decay series has atomic mass numbers with values
evenly divisible by 4. The uranium series featured atomic mass numbers
divisible by 4 with a remainder of 2, and the actinium series had mass
numbers divisible by 4 with a remainder of 3. It was frustrating to be
unable to find a decay series where the mass numbers would be divisible by
4 with a remainder of 1. This frustration was finally relieved with the
discovery of neptunium.