Symbol As

 Atomic Number 33

 Atomic Mass 74.9216

 Electron Configuration [Ar] 3d104s24p3

 Density @ 293 K 5.72 g/cm3

 Melting Point 1090 K

 Boiling Point 886 K (sublimes)

 1st Ionization Energy 946.5 kJ/mole

 Structure Rhombohedral

 Atomic radius 120 pm


H i s t o r y

            Arsenic compounds have been known since the days of Ancient Greece and Rome when arsenic sulfide (As2S3) was used by physicians and poisoners.  Since arsenic can be produced from its ores very easily, many early craftspeople may have seen the element without realizing what it was.  It was first recognized as an element by alchemists. Although it is not certain where and when arsenic was actually discovered, credit for the discovery usually goes to alchemist Albert the Great (Albertus Magnus, 1193-1280).  In 1250 A.D. he heated a common compound of arsenic, As2S3, with soap and formed nearly pure arsenic.  It wasn’t until the mid-seventeenth century that arsenic became well known as an element.   

S o u r c e s

            Arsenic is occasionally found as a free element, but it is usually found in a number of minerals, the most common one being mispickel.  The abundance of arsenic in the Earth’s crust is thought to be about 5 parts per million.  Arsenic can be found in France, Germany, Italy, Romania, Siberia, China, Chile, Mexico, Belgium, Namibia, and the Philippines.  The United States does not produce any arsenic.

G e n e r a l   P r o p e r t i e s

~ Elemental arsenic occurs in two solid modifications: yellow and gray or metallic.  It is a steel gray, very brittle, crystalline, metalloid.

~ Arsenic does not melt when heated.  Instead, it changes directly into a vapor (sublimation).  However, under high pressure, arsenic can be forced to melt at 814 C. 

~ Arsenic is stable in dry air, but the surface oxidizes slowly in moist air to give a bronze tarnish and finally a black covering to the element. 

~ Arsenic does not react with water in the absence of air under normal conditions.

~ When heated in air, arsenic combines with oxygen to form arsenic oxide (As2O3).  A blue flame is produced and the compound gives off a distinctive garlic-like odor.


B i o l o g i c a l   R o l e

            Arsenic may be a necessary ultratrace element for humans.  It is a necessary ultratrace element for red algae, chickens, rats, goats, and pigs.  A deficiency of arsenic results in inhibited growth.


U s e s

            The most infamous use of arsenic is as a poison.  However, arsenic can now be detected during autopsy, so this use of the element has become a legend of the past.  These days the most important use of arsenic is in the preservation of wood.  It is used in the form of a compound called chromated copper arsenate (CCA) and is added to wood used to build houses and other wooden structures.  CCA prevents organisms from growing in the wood and causing it to rot.  Arsenic is also used as a weed killer and rat poison.  Arsenic has been used to improve the roundness of lead shot.  Trace amounts of arsenic are alloyed with lead in storage batteries.  Arsenic is also used in the manufacture of high-efficiency solar cells.  Alloys of gallium, arsenic, and phosphorous are used in the semiconductor industry for the production of light-emitting diodes (LEDs) in watches, clocks, calculators, and numerous other instrument displays.


H a z a r d s  &  R i s k s

            Arsenic compounds are very poisonous to plants and animals. In low doses, arsenic causes nausea, vomiting, and diarrhea.  In larger doses, it results in abnormal heartbeat, damage to blood vessels, and a feeling of “pins and needles” in hands and feet.  Small corns or warts may begin to develop on the palms of the hands and the soles of the feet.  Direct contact with the skin can cause redness and swelling.  Long term exposure can cause cancer.  Inhalation results in lung cancer.  If arsenic is swallowed, cancer may develop in the bladder, kidneys, liver, and lungs.  In large doses, arsenic can be deadly.  Despite the danger of arsenic, it is found in pesticides, wood preservatives, and many household products.


I n t e r e s t i n g   F a c t s

 ~ In its pure form, arsenic costs $320 per 100g.

~ Arsenic compounds were mined by the early Chinese, Greek, and Egyptian civilizations.  No doubt they discovered its toxic properties early on.

~ Arsenic’s name appears to derive from the Latin word arsenicum and the Greek word arsenikos, meaning “masculine” or “male.”  In earlier times it was believed that metals had different sexes.

~ In 1989, the total usage of arsenic in the world was 52,380 tons of As2O3, with approximately 28,530 tons imported by the United States.  Pesticides and wood preservatives accounted for over 80 percent of this use.

~ Arsenic makes up 50 ppb by weight and 4 ppb by atoms in a human being.

~ During the Middle Ages, arsenic compounds were often used to commit murder.  At the time, it was difficult to detect the presence of arsenic in the body, so the person who was murdered was thought to have died of pneumonia