Merck KGaA (Darmstadt, Germany)
EMD PTE
You can't tell by the title, but this is a functional periodic table of elements. Incorporating bright colors, lucid text, and easily operated features, this application serves as a valuable reference tool for your chemistry class.
Other
Chemical Elements: Potassium
A nice, clear site, containing a good deal of elemental information, including atomic weight, density, boiling point, isotopes and more. An image shows the electron energy levels for the element.
Other
Chemical Elements: Plutonium
A nice, clear site, containing a good deal of elemental information, including; atomic weight, density, boiling point, isotopes and more. An image shows the electron energy levels for the element.