Georgia State University
Georgia State University: Hyper Physics: Neptunium
Good information on neptunium, all nicely arranged.
Florida-Spectrum Environmental Services
Florida Spectrum: Chemical Fact Sheet: Neptunium
This site provides a fact sheet with information on the basic data and properties of Neptunium. It also includes some of its uses.
Chemicool
Chemicool: Neptunium
This Chemicool site offers excellent data tables with known information on Neptunium.
Royal Society of Chemistry
Chemical Society: Neptunium
Short summary of basic information on neptunium.
Web Elements
Web Elements Periodic Table: Neptunium
WebElements provides a very good source of basic information on neptunium, including physical properties, isotopes and electron configuration.
Other
Lanl: The Actinide Research Quarterly
This is "The Actinide Research Quarterly", a publication about current research of the actinide metals and nuclear materials technology by Los Alamos National Laboratory. Very detailed information.
Corrosion Source
Corrosion Source: Neptunium
Easy to follow information on the history, sources, properties and isotopes of neptunium.
Curated OER
[Bohr Model of Neptunium]
This site provides information about the element Neptunium (Np), and includes its atomic structure, isotopes, and other facts.