Arsenic is an element, so it's chemical formula is the same as it is on the periodic table, which is As.
The physical properties of arsenic are that it is shiny, magnetic, and soluble in water.
The chemical properties of arsenic are that it will bind to an animal's body and release toxins found in metals naturally.
Arsenic occurs naturally and is generally found beneath groundwater.
Arsenic can be inhaled through cigarettes, so it takes large levels of accumulation to take effect.
Source: http://www.greenfacts.org/en/arsenic/index.htm#1
