Web Elements
Web Elements Periodic Table: Potassium
This WebElements site provides a great deal of elemental information. There are audio files demonstrating the correct pronunciation of the element name, pictures showing the electron shells, and information on isotopes, properties and more.
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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.