The Arsenic reference article from the English Wikipedia on 24-Jul-2004
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Arsenic

See the real Africa
germaniumarsenicselenium
P
Ar
Sb  
 
 
Image:As-TableImage.png
General
Name, Symbol, Numberarsenic, As, 33
Series metalloids
Group, Period, Block15 (VA), 4 , p
Density, Hardness 5727 kg/m3, 3.5
Appearance metallic grey
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Atomic properties
Atomic weight 74.92160 amu
Atomic radius (calc.) 115 (114) pm
Covalent radius 119 pm
van der Waals radius 185 pm
Electron configuration [Ar]33d10 4s2 4p3
e- 's per energy level2, 8, 18, 5
Oxidation states (Oxide) +-3,5 (mildly acidic)
Crystal structure rhombohedral
Physical properties
State of matter solid
Melting point 1090 K (1503 ðF)
Boiling point 887 K (1137 ðF)
Molar volume 12.95 ×1010-6 m3/mol
Heat of vaporization 34.76 kJ/mol
Heat of fusion 369.9 kJ/mol
Vapor pressure __ Pa at __ K
Speed of sound __ m/s at __ K
Miscellaneous
Electronegativity 2.18 (Pauling scale)
Specific heat capacity 330 J/(kg*K)
Electrical conductivity 3.45 106/m ohm
Thermal conductivity 50 W/(m*K)
1st ionization potential 947.0 kJ/mol
2nd ionization potential 1798 kJ/mol
3rd ionization potential 2735 kJ/mol
4th ionization potential 4837 kJ/mol
5th ionization potential 6043 kJ/mol
6th ionization potential 12310 kJ/mol
Most stable isotopes
isoNAhalf-life DMDE MeVDP
75As100%As is stable with 42 neutrons
SI units & STP are used except where noted.

Arsenic is a chemical element in the periodic table that has the symbol As and atomic number 33. This is a notorious poisonous metalloid that has three allotropic forms; yellow, black and grey. Arsenic and its compounds are used as pesticides, herbicides and insecticides and various alloys.

Table of contents
1 Notable characteristics
2 Applications
3 History
4 Occurrence
5 Precautions
6 Related topics
7 Reference
8 External links

Notable characteristics

Arsenic is chemically very similar to its predecessor phosphorus, so much so that it will partly substitute for it in biochemical reactions and is thus poisonous. When heated it rapidly oxidizes to arsenous oxide, which has a garlic odor. Arsenic and some arsenic compounds can also sublime upon heating, converting to gaseous form directly. Elemental arsenic is found in two solid forms: yellow and gray/metallic, with specific gravities of 1.97 and 5.73, respectively.

Applications

Lead arsenate has been used, well into the 20th century, as a pesticide on fruit trees (resulting in neurological damage to those working the sprayers), and copper arsenate has even been recorded in the 19th century as a coloring agent in sweets. Other uses;

History

Arsenic (
Greek arsenikon, meaning "yellow orpiment") has been known and used since ancient times. It has been frequently used for murder, the symptoms of arsenic poisoning being somewhat ill-defined, until the advent of the Marsh test, a sensitive chemical test for its presence.

Albertus Magnus is believed to have been the first to isolate the element in 1250. In 1649 Johann Schroeder published two ways of preparing arsenic.

Alchemical symbol for arsenic
alchemical symbol for arsenic is shown opposite.

There is a massive epidemic of arsenic poisoning in Bangladesh. This is due to the massive tube well drinking-water program instigated by western NGOss in the late twentieth century, who failed to test for arsenic in the groundwater. Hundreds of thousands of people are affected. It is thought to be the worst mass-poisoning in history, and possibly the worst environmental disaster in history.

Occurrence

Arsenopyrite also called mispickel (FeSAsAs) is the most common mineral from which, on heating, the arsenic sublimes leaving ferrous sulfide.

The most important compounds of arsenic are white arsenic, its sulfide, Paris green, calcium arsenate, and lead arsenate. Paris green, calcium arsenate, and lead arsenate have been used as agricultural insecticides and poisons. It is sometimes found native, but usually combined with silver, cobalt, nickel, iron, antimony, or sulfur.

Precautions

Arsenic and many of its compounds are especially potent poisons. Arsenic kills by massively disrupting the digestive system, leading to death from shock. See arsenic poisoning.

Related topics

Reference

External links