Arsenic (33)

Arsenic and its compounds are poisonous as any reader of "who-done-it" books knows. Upon heating arsenic and some minerals containing arsenic, it sublimes (transfers from the solid to the gaseous state, without passing through the liquid state).

•Name: Arsenic
•Symbol: As
•Atomic number: 33
•Atomic weight: 74.92160
•Standard state: solid at 298 K
•CAS Registry ID: 7440-38-2
•Group in periodic table: 15
•Group name: Pnictogen
•Period in periodic table: 4
•Block in periodic table: p-block
•Color: metallic grey
•Classification: Semi-metallic

Historical information

Arsenic was discovered by Known since ancient times at no data in not known. Origin of name is from the Greek word "arsenikon" meaning "yellow orpiment". Arsenic compounds were mined by the early Chinese, Greek and Egyptian civilizations. No doubt they discovered its toxic properties early on.

It is believed that Albertus Magnus obtained the element in 1250 A.D. who obtained it by heating soap together with orpiment (arsenic trisulphide, As2S3).

Arsenic is one of the elements which has an alchemical symbol (alchemy is an ancient pursuit concerned with, for instance the transformation of other metals into gold), which is two circles joined by a line.

Physical properties

•Melting point: 1090 [or 817 °C (1503 °F)] (under pressure) K
•Boiling point: 887 [or 614 °C (1137 °F)] (sublimes) K
•Density of solid: 5727 kg m-3

Orbital properties

•Ground state electron configuration: [Ar].3d10.4s2.4p3
•Shell structure: 2.8.18.5
•Term symbol: 4S3/2

Isolation

It is not usually necessary to make arsenic in the laboratory as it is commercially available. Arsenic is found in nature in a number of minerals including realgar (As4S4), orpiment (As2S3), arsenolite (As2O3), and iron minerals such as arsenopyrite (FeAsS) and loellingite (FeAs2). Arsenic is made on an industrial scale by heating appropriate minerals in the absence of air. The arsenic is condensed out as a solid.

FeAsS (700°C) → FeS + As(g) → As(s)

Interesting Facts about Arsenic:

•Arsenic (English/French) Arsen (German) Arsenico (Italian) Arsénico (Spanish) Arsenik (Swedish)

•Arsenic is found naturally in a common mineral called Arsenopyrite or Mispickel (FeSAs). It is also found in arsenides of metals such as silver, cobalt and nickel. Apart from these inorganic forms, arsenic is found in food, water and air also.

•Arsenic is located in the Groups 13,14,15,16 and 17 of the Periodic Table and hence, is classified as a metalloid element. Thus, it has the properties of both metals and non-metals.

•The most common grey arsenic has a metallic sheen and conducts electricity. Yellow arsenic is metastable, a poor electrical conductor and does not have a metallic sheen. Black arsenic is glassy, brittle and a poor electrical conductor.

•Due to its high level of toxicity, arsenic has been named as the ‘Kings of Poison’. Hence, for the same reason, it is used as a wood preservative against insects, bacteria and fungi. It also finds its use in making insecticides, poison, weed killers, etc.

•Arsenic, in the form of Gallium arsenide, is used in lasers that are employed to convert electricity into coherent light.

•Arsenic is used in ammunition manufacturing, since it helps to create harder and rounder bullets.

•The top producers of arsenic are China, Peru, Chile and Morocco. While the production from Peru comes from copper mining, production in China comes from mining of gold.

•Pure arsenic is less dangerous than arsenic compounds, such as AsH3 and As2O3, which are absorbed easily and are carcinogenic with high toxicity.

•In the 18th, 19th and 20th century, arsenic was used in the form of medicines, two most common being arsphenamine and arsenic trioxide. While the former medication was prescribed for syphilis and trypanosomiasis, the latter one was useful in treating cancer.

•Some of the side effects of arsenic include agitation, constipation, darkening of skin, drowsiness, earache, poor appetite, increased sweating, mouth sores, fatigue, weight loss, nausea, nose bleeding, vomiting, depression, seizures, tremors, dry eyes, allergic reactions, sudden weight gain, wheezing, irregular pulse and increased thirst.