* Arsenic is a member of the semi-metals family:
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ARSENIC / As / 33
Arsenic is found in two forms: gray, which has metallic properties,
and yellow, which does not. They have different densities. The
gray form is brittle, tarnishes and burns in oxygen. The yellow
form is less reactive, dissolving only when heated in strong acids
and alkalis. Only one isotope is found in nature, As<75/33>;
it is stable.
atomic weight: 74.92160
abundance: 53rd
density: 1.97 gm/cc (gray arsenic)
density: 5.73 gm/cc (yellow arsenic)
melting point: doesn't melt, subliming at 616 C
valence: -3 <3> 5
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Arsenic is dangerously toxic in any more than trace doses, having once been used in insecticides, but it has medicinal uses when employed in small quantities. Arsenic is produced in tens of thousands of tonnes a year; its industrial uses are specialized, the material being used in certain types of glass, as a wood preservative, and in semiconductor devices in the form of gallium arsenide (GaAs).
One of the odd facts about arsenic is that the body can build up a tolerance to it over time. There are towns where the water supply is contaminated with arsenic, making it very dangerous to outsiders, while the locals drink it without the slightest ill effect.
