8.TT.1.3 Arsenic PowerPoint

By: Maleek Walker Chemistry Exit Project

Arsenic Background

• Arsenic is a naturally occurring substance. It occurs in several forms, often in compounds with other chemical elements. Arsenic and all of its compounds are poisonous but the toxicity varies. For example, inorganic arsenic - arsenic combined with oxygen, chlorine or sulfur - is thought to be the most toxic, while most organic forms of arsenic are relatively less toxic. In its solid state arsenic appears as a silver-gray, brittle semi-metal that tarnishes in the air. It is about the 52nd most common chemical element on the earth.

Where Is Arsenic Found?

• 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).

Arsenic In Everyday Life

• The most widely known use of arsenic is as a poison. It is used in bug, weed, and rat poisons. It is also highly toxic to humans and can cause cancer when it comes in contact with humans. If ingested in small amounts over time, it will produce the symptoms of pneumonia and the victim will die with hardly a trace Of arsenic in his body. Coroners today have ways of detecting the smallest amounts in an autopsy, so arsenic is rarely used for poisoning people anymore. It was discovered that Napoleon Bonaparte might have died from arsenic poisoning. Massive amounts of arsenic were found in his hair structure. The dye in the wallpaper of his room large amounts of arsenic, and the damp may have created a deadly gas which he inhaled.

Properties In Arsenic

• The element is a steel gray, very brittle, crystalline, semimetallic solid; it tarnishes in air, and when it is heated it rapidly oxidizes to arsenous oxide, which smells of garlic. Elemental arsenic occurs in two solid modifications: yellow, and gray or metallic, with specific gravities of 1.97, and 5.73, respectively. Arsenic and its compounds are poisonous.

Interesting facts on Arsenic• 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

Arsenic Being Deadly

• 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.

Biological Role

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

Arsenic Sources

• It is sometimes found native, but usually combined with silver, cobalt, nickel, iron, antimony, or sulfur. Arsenopyrite also called mispickel is the most common mineral from which, on heating, the arsenic sublimes leaving ferrous sulfide.

Arsenic Make-up• 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