Further information Description Selenium can be prepared with either an amorphous or crystalline structure.
Elemental selenium is relatively nontoxic and is considered to be an essential trace element.
Hydrogen selenide in a concentration of 1.5 ppm is intolerable to man. Both values are quoted on the Pauling scale. For most elements, the most stable allotrope is illustrated. This section gives some data for naturally occurring isotopes. Copyright 1997 Mark Winter Department of Chemistry at the University of Sheffield , Sheffield S3 7HF, England.