Name       : Arsenic
Symbol     : As
Atomic #   : 33
Atom weight: 74.9216
Melting P. : 817
Boiling P. : 613
Oxidation  : +3, -3, +5
Pronounced : AR-s'n-ik
From       : Latin arsenicum, and Greek, arsenikon: both are names for a
             popular pigment, yellow orpiment
Identified : Possibly by Albertus Magnus in 1250 A.D.
Appearance : Steel gray, brittle semimetal
Note       : Popularly known for its highly poisonous compounds
             
[Properties]

  Arsenic is a semimetal, or metalloid element. It isn't quite a metal such
as aluminum or tin, and it isn't quite a nonmetal such as sulfur and bromine.
It belongs to a fairly small group of semimetal that share the same general
area on the periodic table of the elements.
  The principal allotrope of the arsenic is gray arsenic. This is 
characterized as a brittle, silvery-gray metal. Two other allotropes,
yellow and black arsenic, are unstable crystalline substances that can be
produced by first heating, then cooling, gray arsenic. Gray arsenic tends
to sublimate rather than go through a molten state. Heating gray arsenic to
its sublimation temperature, 613 degrees, causes it to generate an arsenic
vapor. If you cool this vapor slowly, you will see the black form of 
arsenic condensing on the sample. As the sample continues to cool and 
passes through the 360 degrees mark, the blakc arsenic changes back to the
gray form.
  Cooling gray arsenic rapidly from its sublimation temperature, however,
causes yellow arsenic to condense on the sample. Unlike black arsenic, the
yellow attotrope does not automatically return to the gray form upon 
further cooling. The yellow allotrope is stable with respect to changes in
temperature but is sensitive to light. Light energy converts yellow arsenic
to the stable gray form.