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About Arsenic

Arsenic Bohr

The discovery of arsenic is generally attributed to Saint Albertus Magnus, sometimes known as Albert the Great, as there are records of the bishop, scholar, and alchemist producing elemental arsenic in 1250 AD. However, arsenic compounds have been known since antiquity, and earlier alchemists may have accomplished this feat as well. Whereas many more recently discovered elements have names with Greek roots, arsenic’s roots are older, as the Greek arsenikon was derived from Syriac and Persian words for “yellow orpiment”, which is a naturally occurring arsenic sulfide mineral. The name came into Latin as arsenicum, and to old French as arsenic, which was adopted as the English word for the element.

Arsenic’s cultural history is curiously paradoxical, as it has been used as both medicine and poison for centuries. Hippocrates prescribed orpiment for ulcers, and ancient Chinese medicine used arsenic compounds to treat a variety of ailments. In the 18th century, Thomas Fowler made popular the patent medicine “Fowler’s solution”, a liquid formulation of potassium arsenite that was sold as a remedy for complaints as diverse as asthma, eczema, and malaria. At the same time, arsenic compounds were well known as poisons that they were used to kill pests and people in medieval Europe. The French knew arsenic trioxide, an odorless compound that easily mixed into food or drink, as “poudre de succession”--”Inheritance powder”, because it was used so commonly used in homicides.

Intentional arsenic poisonings became less common after a reliable method for detecting arsenic in a diseased person, the Marsh test, was introduced in 1836, but many modern uses of the element continued to take advantage of its toxicity. A variety of arsenic compounds have been used as pesticides and herbicides and in wood preservatives, though the toxicity of such products to the humans working with them has led to their replacement by safer alternatives for some applications. The deadly properties of arsenic have even been weaponized--a number of chemical agents used in the first world war were arsenic compounds, and Agent Blue, one of the “rainbow herbicides” used in the Vietnam war, was a potent arsenic herbicide.

Arsenic-basedmedical treatments also have modern counterparts. An arsenic containing drug called Salvarsan was developed as a syphilis treatment in the early 20th century, and remained in use until penicillin became available in the 1940s. The arsenic containing drug Melarsoprol is still sometimes used as a treatment for late stages of African trypanosomiasis--known colloquially as African sleeping sickness--despite significant side effects related to arsenic toxicity. Arsenic is also used in the treatment of several cancers, particularly in recurrences of acute promyelocytic leukemia following first line treatments.

A third historical use for arsenic was in metal alloys. Early bronze was made from arsenic and copper; it was only later that tin replaced arsenic. Brass even today sometimes contain arsenic, which lessens corrosive loss of zinc from the copper-zinc alloy. The primary modern use of arsenic in alloys, however, is in lead alloys. The addition of arsenic makes lead, a soft metal, significantly harder, and such alloys are used in standard lead-acid car batteries.

Other modern uses of arsenic have no historical precedent; a prime example is arsenic’s use in semiconductors. Arsenic is a component of many III-V type semiconductors as well as semiconducting compounds with more complex formulations. The most common III-V semiconductor is gallium arsenide. Gallium arsenide was developed in the 1960s as a semiconductor with somewhat different electrical properties than the more common silicon, and that is more suited than silicon to some applications. Notably, gallium arsenide is a direct band gap semiconductor, which means that it can both absorb and emit light with high efficiency. This lends it to use in LEDs and lasers. Additionally, extremely thin layers of gallium arsenide can be used to effectively absorb all the photons from incident sunlight, as opposed to the thick layers of silicon required for the same task. This allows for the creation of one type of thin-film photovoltaic cell. GaAs-based semiconductor devices also exhibit less noise than those produced from silicon, and are thus favored in many telecommunications applications. The other III-V arsenic semiconductors have similar uses to gallium arsenide, and semiconductors with more complex formulations are generally used in settings where the ability to tune the material’s band gap through adjustments to the precise molecular composition are desirable.

In nature, arsenic is most commonly found in minerals in combination with sulfur and sometimes iron, nickel, or copper. The two forms of arsenic sulfide, realgar and orpiment, were often used as sources of arsenic in antiquity. The most common form of arsenic used in industry is arsenic trioxide, which may be produced by roasting any of these minerals in air. Roasting the same minerals without oxygen present will produce metallic arsenic. Arsenic is rarely harvested directly, but rather produced as a side product of the mining and purification of other metal ores.

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Elemental Arsenic Picture

Summary. Arsenic has numerous applications as a semiconductor and other electronic applications as Indium arsenide, silicon arsenide and tin arsenide. Arsenic is finding increasing uses as a doping agent in solid-state devices such as transistors. Gallium arsenideHigh Purity (99.99999%) Arsenic (As) Sputtering Target is a semiconductor material frequently used in optoelectronic applications. Arsenic is used in bronzing and for hardening and improving the sphericity of shot. Due to their toxicity, arsenic compounds are used in insecticides and wood preservation. High Purity (99.9999%) Arsenic Oxide (As2O3) PowderArsenic is available as metal and compounds with purities from 99% to 99.999% (ACS grade to ultra-high purity). Elemental or metallic forms include pellets, rod, wire and granules for evaporation source material purposes. Arsenic oxides are insoluble arsenic compounds available in powder and dense pellet form for such uses as optical coating and thin film applications. Arsenic is also available in soluble forms including chlorides, and acetates. These compounds can be manufactured as solutions at specified stoichiometries.

Arsenic Properties

Arsenic (As) atomic and molecular weight, atomic number and elemental symbolArsenic is a Block P, Group 15, Period 4 element.Elemental Arsenic Arsenic Bohr ModelThe number of electrons in each of Arsenic's shells is 2, 8, 18, 5 and its electron configuration is [Ar] 3d10 4s2 4p3.The arsenic atom has a radius of and its Van der Waals radius is In its elemental form, CAS 1327-53-3, arsenic has a metallic grey appearance. Arsenic is found in numerous minerals including arsenolite (As2O3), arsenopyrite (FeAsS), loellingite (FeAs2), orpiment (As2S3), and realgar (As4S4). Arsenic was discovered in the early Bronze Age, circa 2500 BC. It was first isolated by Albertus Magnus in 1250.

Symbol: As
Atomic Number: 33
Atomic Weight: 74.92
Element Category: metalloid
Group, Period, Block: 15 (pnictogens), 4, p
Color: metallic gray/ gray
Other Names: Arsen, Arsenico, Arsenik
Melting Point: 616 °C, 1140.8 °F, 889.15 K
Boiling Point: Sublimes
Density: 5.778 kg·m3
Liquid Density @ Melting Point: 5.22 g/cm3
Density @ 20°C: 5.776 g/cm3
Density of Solid: 5727 kg·m3
Specific Heat: 0.328 kJ/kg/K
Superconductivity Temperature: N/A
Triple Point: 1090 K, 3628 kPa
Critical Point: 1673 K,  MPa
Heat of Fusion (kJ·mol-1): 27.7
Heat of Vaporization (kJ·mol-1): 31.9
Heat of Atomization (kJ·mol-1): 301.42
Thermal Conductivity: W/cm/ K @ 298.2 K
Thermal Expansion: N/A
Electrical Resistivity: 260 nΩ·m at 0°C
Tensile Strength: N/A
Molar Heat Capacity: 24.64 J·mol-1·K-1
Young's Modulus: 8 GPa
Shear Modulus: N/A
Bulk Modulus: 22 GPa
Poisson Ratio: N/A
Mohs Hardness: 3.5
Vickers Hardness: N/A
Brinell Hardness: 1440 MPa
Speed of Sound: N/A
Pauling Electronegativity: 2.18
Sanderson Electronegativity: 2.82
Allred Rochow Electronegativity: 2.2
Mulliken-Jaffe Electronegativity: 2.26 (20% s orbital)
Allen Electronegativity: 2.211
Pauling Electropositivity: 1.82
Reflectivity (%): N/A
Refractive Index: 1.001552 
Electrons: 33
Protons: 33
Neutrons: 42
Electron Configuration: [Ar] 3d10 4s2 4p3
Atomic Radius: 119 pm
Atomic Radius,
non-bonded (Å):
Covalent Radius: 119±4 pm
Covalent Radius (Å): 1.2
Van der Waals Radius: 185 pm
Oxidation States: 5, 3, -3
Phase: Solid
Crystal Structure: simple trigonal
Magnetic Ordering: diamagnetic
Electron Affinity (kJ·mol-1) 77.574
1st Ionization Energy: 944.46 kJ·mol-1
2nd Ionization Energy: 1797.82 kJ·mol-1
3rd Ionization Energy: 2735.48 kJ·mol-1
CAS Number: 7440-38-2
EC Number: 231-148-6
MDL Number: MFCD00085309
Beilstein Number: N/A
SMILES Identifier: [AsH3]
InChI Identifier: InChI=1S/As
PubChem CID: 5359596
ChemSpider ID: 4514330
Earth - Total:  3.2 ppm 
Mercury - Total: 6.4 ppm
Venus - Total: 3.1 ppm
Earth - Seawater (Oceans), ppb by weight: 2.3
Earth - Seawater (Oceans), ppb by atoms: 0.19
Earth -  Crust (Crustal Rocks), ppb by weight: 2100
Earth -  Crust (Crustal Rocks), ppb by atoms: 580
Sun - Total, ppb by weight: N/A
Sun - Total, ppb by atoms: N/A
Stream, ppb by weight: 1
Stream, ppb by atoms: 0.01
Meterorite (Carbonaceous), ppb by weight: 1800
Meterorite (Carbonaceous), ppb by atoms: 460
Typical Human Body, ppb by weight: 50
Typical Human Body, ppb by atom: 4
Universe, ppb by weight: 8
Universe, ppb by atom: 0.1
Discovered By: Ancients
Discovery Date: Bronze Age circa 2500 BC
First Isolation: Albertus Magnus (1250)

Health, Safety & Transportation Information for Arsenic

Though inorganic Arsenic is extremely toxic, even in very small amounts, other forms of arsenic have proven safe and even potentially beneficial to humans. Safety data for Arsenic and its compounds can vary widely depending on the form. For potential hazard information, toxicity, and road, sea and air transportation limitations, such as DOT Hazard Class, DOT Number, EU Number, NFPA Health rating and RTECS Class, please see the specific material or compound referenced in the Products tab. The below information applies to elemental (metallic) Arsenic.

Safety Data
Material Safety Data Sheet MSDS
Signal Word Danger
Hazard Statements H301-H331-H410
Hazard Codes T, N
Risk Codes 23/25-50/53
Safety Precautions 20/21-28-45-60-61
RTECS Number CG0525000
Transport Information UN 1558 6.1/PG 2
WGK Germany 3
Globally Harmonized System of
Classification and Labelling (GHS)
Skull and Crossbones-Acute Toxicity  Environment-Hazardous to the aquatic environment

Arsenic Isotopes

Arsenic has one stable isotope: 75As.

Nuclide Isotopic Mass Half-Life Mode of Decay Nuclear Spin Magnetic Moment Binding Energy (MeV) Natural Abundance
(% by atom)
60As 59.99313(64)# UnKnown p to 59Ge 5+# N/A 454.22 -
61As 60.98062(64)# UnKnown p to 60Ge 3/2-# N/A 474.41 -
62As 61.97320(32)# UnKnown p to 61Ge 1+# N/A 489.01 -
63As 62.96369(54)# UnKnown p to 62Ge (3/2-)# N/A 506.4 -
64As 63.95757(38)# 40(30) ms [18(+43-7) ms] p to 63Ge 0+# N/A 520.07 -
65As 64.94956(32)# 170(30) ms ß+ to 64Ge 3/2-# N/A 535.6 -
66As 65.94471(73) 95.77(23) ms ß+ to 65Ge (0+) N/A 548.34 -
67As 66.93919(11) 42.5(12) s ß+ to 66Ge (5/2-) N/A 561.07 -
68As 67.93677(5) 151.6(8) s EC to 68Ge 3+ N/A 571.95 -
69As 68.93227(3) 15.2(2) min EC to 69Ge 5/2- 1.2 583.75 -
70As 69.93092(5) 52.6(3) min EC to 70Ge 4(+#) 2.1061 593.7 -
71As 70.927112(5) 65.28(15) h EC to 71Ge 5/2- 1.6735 604.57 -
72As 71.926752(5) 26.0(1) h EC to 72Ge 2- -2.1566 613.58 -
73As 72.923825(4) 80.30(6) d EC to 73Ge 3/2- N/A 624.45 -
74As 73.9239287(25) 17.77(2) d ß- to 74Se; EC to 74Ge 2- -1.597 632.53 -
75As 74.9215965(20) STABLE ß- to 76Se 3/2- -0.906 642.47 -
76As 75.922394(2) 1.0942(7) d - 2- 1.43947 649.62 100
77As 76.9206473(25) 38.83(5) h ß- to 77Se 3/2- N/A 659.56 -
78As 77.921827(11) 90.7(2) min ß- to 78Se 2- N/A 666.71 -
79As 78.920948(6) 9.01(15) min ß- to 79Se 3/2- N/A 675.72 -
80As 79.922534(25) 15.2(2) s ß- to 80Se 1+ N/A 681.94 -
81As 80.922132(6) 33.3(8) s ß- to 81Se 3/2- N/A 690.01 -
82As 81.92450(21) 19.1(5) s ß- to 82Se (1+) N/A 696.23 -
83As 82.92498(24) 13.4(3) s ß- to 83Se 3/2-# N/A 704.31 -
84As 83.92906(32)# 4.02(3) s ß- to 84Se; ß- + n to 83Se (3)(+#) N/A 707.73 -
85As 84.93202(21)# 2.021(10) s ß- + n to 84Se; ß- to 85Se (3/2-)# N/A 713.01 -
86As 85.93650(32)# 0.945(8) s ß- to 86Se; ß- + n to 85Se N/A N/A 717.37 -
87As 86.93990(32)# 0.56(8) s ß- to 87Se; ß- + n to 86Se 3/2-# N/A 722.65 -
88As 87.94494(54)# 300# ms [>300 ns] ß- to 88Se; ß- + n to 87Se N/A N/A 726.07 -
89As 88.94939(54)# 200# ms [>300 ns] ß- to 89Se 3/2-# N/A 729.49 -
90As 89.95550(86)# 80# ms [>300 ns] Unkown N/A N/A 731.98 -
91As 90.96043(97)# 50# ms [>300 ns] Unkown 3/2-# N/A 735.4 -
92As 91.96680(97)# 30# ms [>300 ns] Unkown N/A N/A 737.89 -