The Handbook
is a program which shows you the Periodic System of the elements (PSE). You can use to search for information about the elements or to learn facts about the PSE.

Introduction
provides you with all kind of information about the PSE (Periodic System of Elements.) You can lookup lots of information about the elements and also use visualisations to show them. If the information provided by are not sufficient for you you can look up more via the internet. It is free and licensed under the Public License.