Chemical information database of over 380,000 chemicals, synonyms, structures, regulatory list information, and links to other databases. Links to the Drug Information Portal. Maintained by the U.S. National Library of Medicine.
Clicking on an element displays more complete physical and chemical properties in sections including States, Energies, Appearances and Characteristics, Uses, Reactions, Compounds, Radius, Conductivity, and Abundance and Isotopes. Many elements offer links to interesting YouTube demonstrations.