Arsenic is an inorganic chemical element that is a part of the trioxide family of elements. Arsenic is found in many minerals and metals, and it can be found in its natural form as well as in the pure state. Arsenic trioxide is a chemical compound that is an inorganic compound made up of arsenic and oxygen. Arsenic trioxide is used in many products including pesticides, herbicides, wood preservatives, and antidandruff shampoos.