Introduction
Group: 15 or V A
Atomic Weight: 74.9216
Period: 4
CAS Number: 7440-38-2
Classification
No Stable Isotopes
Solid
Liquid
Gas
Solid (Predicted)
Description • Uses/Function
Elemental arsenic occurs in twosolid modifications: yellow, and gray or metallic, with specific gravities of 1.97, and 5.73, respectively. Gray arsenic, the ordinary stable form, hasa m.p. of 817°C (28 atm) and sublimes at 614°C. Several other allotropic forms of arsenic are reported in the literature. It is believed that AlbertusMagnus obtained the element in 1250 A.D. In 1649 Schroeder published two methods of preparing the element. It is found native, in the sulfides realgarand orpiment, as arsenides and sulfarsenides of heavy metals, as the oxide, and as arsenates. Mispickel, arsenopyrite, (FeSAs) is the most commonmineral, from which on heating the arsenic sublimes leaving ferrous sulfide. The element is a steel gray, very brittle, crystalline, semimetallic solid;it tarnishes in air, and when heated is rapidly oxidized to arsenous oxide (As2O3) with the odor of garlic. Arsenic and its compounds are poisonous.These values, however, are being studied, and may be lowered. Arsenic is also used in bronzing, pyrotechny, and for hardening and improving thesphericity of shot. The most important compounds are white arsenic (As2O3), the sulfide, Paris green 3Cu(AsO2)2 · Cu(C2H3O2)2, calcium arsenate,and lead arsenate; the last three have been used as agricultural insecticides and poisons. Marsh’s test makes use of the formation and readydecomposition of arsine (AsH3). Arsenic is available in high-purity form. It is finding increasing uses as a doping agent in solid-state devices suchas transistors. Gallium arsenide is used as a laser material to convert electricity directly into coherent light. Natural arsenic is made of one isotope 75As.Twenty-five other radioactive isotopes and isomers are known. Arsenic (99%) costs about $175/kg. Purified arsenic (99.9995%) costs about $2/gm. 1
• "amino acid metabolism" 2
• "Farmers using arsenic as an insecticide often suffer from skin and lung cancers." 3
Physical Properties
Melting Point:4*
Electron Configuration: [Ar] 4s2 3d10 4p3
n = 4
Electronegativity (Pauling scale):6 2.18
Specific Heat: 0.329 J/g°C 10 = 24.649 J/mol°C = 0.079 cal/g°C = 5.891 cal/mol°C
2 AsH3 (g) → 2 As (s) + 3 H2 (g) 15
Earth - Source Compounds: sulfides 17
External Links:
(1) - Lide, David R. CRC Handbook of Chemistry and Physics, 83rd ed.; CRC Press: Boca Raton, FL, 2002; p 4:4.
Boiling Point:4*
Sublimation Point:4 603 °C = 876.15 K = 1117.4 °F
Triple Point:4 817 °C = 1090.15 K = 1502.6 °F at 3.70 MPa
Critical Point:4 1400 °C = 1673.15 K = 2552 °F 4
Density:5 5.75 g/cm3
* - at 1 atm
Electron Configuration
Block: p
Highest Occupied Energy Level: 4
Valence Electrons: 5
Quantum Numbers:
ℓ = 1
mℓ = 1
ms = +½
Bonding
Electropositivity (Pauling scale): 1.82
Electron Affinity:7 0.814 eV
Oxidation States: ±3,+5
Work Function:8 3.75 eV = 6.0075E-19 J
Ionization Potential
eV 9
kJ/mol
1
9.7886
944.5
2
18.633
1797.8
Ionization Potential
eV 9
kJ/mol
3
28.351
2735.5
4
50.13
4836.8
Ionization Potential
eV 9
kJ/mol
5
62.63
6042.9
6
127.6
12311.5
Thermochemistry
Thermal Conductivity: 50 (W/m)/K, 27°C 11
Heat of Fusion:
Heat of Vaporization: 34.76 kJ/mol 12 = 464.0 J/g
State of Matter
Enthalpy of Formation (ΔHf°)13
Entropy (S°)13
Gibbs Free Energy (ΔGf°)13
(kcal/mol)
(kJ/mol)
(cal/K)
(J/K)
(kcal/mol)
(kJ/mol)
(s alpha-gray)
0
0
8.4
35.1456
0
0
Isotopes
Nuclide
Mass 14
Half-Life 14
Nuclear Spin 14
Binding Energy
60As
59.99313(64)#
5+#
464.98 MeV
61As
60.98062(64)#
3/2-#
485.16 MeV
62As
61.97320(32)#
1+#
499.75 MeV
63As
62.96369(54)#
(3/2-)#
517.14 MeV
64As
63.95757(38)#
40(30) ms [18(+43-7) ms]
0+#
530.80 MeV
65As
64.94956(32)#
170(30) ms
3/2-#
546.32 MeV
66As
65.94471(73)
95.77(23) ms
(0+)
559.05 MeV
67As
66.93919(11)
42.5(12) s
(5/2-)
571.78 MeV
68As
67.93677(5)
151.6(8) s
3+
582.65 MeV
69As
68.93227(3)
15.2(2) min
5/2-
594.44 MeV
70As
69.93092(5)
52.6(3) min
4(+#)
604.38 MeV
71As
70.927112(5)
65.28(15) h
5/2-
615.24 MeV
72As
71.926752(5)
26.0(1) h
2-
624.25 MeV
73As
72.923825(4)
80.30(6) d
3/2-
635.11 MeV
74As
73.9239287(25)
17.77(2) d
2-
643.18 MeV
75As
74.9215965(20)
STABLE
3/2-
653.12 MeV
76As
75.922394(2)
1.0942(7) d
2-
660.26 MeV
77As
76.9206473(25)
38.83(5) h
3/2-
670.19 MeV
78As
77.921827(11)
90.7(2) min
2-
677.33 MeV
79As
78.920948(6)
9.01(15) min
3/2-
686.34 MeV
80As
79.922534(25)
15.2(2) s
1+
692.54 MeV
81As
80.922132(6)
33.3(8) s
3/2-
700.61 MeV
82As
81.92450(21)
19.1(5) s
(1+)
706.82 MeV
83As
82.92498(24)
13.4(3) s
3/2-#
714.89 MeV
84As
83.92906(32)#
4.02(3) s
(3)(+#)
718.31 MeV
85As
84.93202(21)#
2.021(10) s
(3/2-)#
723.59 MeV
86As
85.93650(32)#
0.945(8) s
727.93 MeV
87As
86.93990(32)#
0.56(8) s
3/2-#
733.21 MeV
88As
87.94494(54)#
300# ms [>300 ns]
736.62 MeV
89As
88.94939(54)#
200# ms [>300 ns]
3/2-#
740.04 MeV
90As
89.95550(86)#
80# ms [>300 ns]
742.52 MeV
91As
90.96043(97)#
50# ms [>300 ns]
3/2-#
745.93 MeV
92As
91.96680(97)#
30# ms [>300 ns]
748.41 MeV
Values marked # are not purely derived from experimental data, but at least partly from systematic trends. Spins with weak assignment arguments are enclosed in parentheses. 14
Reactions
2 As (s) + 3 Cl2 (g) → 2 AsCl3 (ℓ) 16
3 As (s alpha-gray) + 5 HNO3 (aq) + 2 H2O (ℓ) → 3 H3AsO4 (aq) + 5 NO (g)
Abundance
Earth - Seawater: 0.0037 mg/L 18
Earth -
Crust:
1.8 mg/kg = 0.00018% 18
Earth -
Total:
3.2 ppm 19
Mercury -
Total:
6.4 ppm 19
Venus -
Total:
3.1 ppm 19
Chondrites - Total: 4.6 (relative to 106 atoms of Si) 20
Compounds
arsenic dioxide
arsenic diphosphide
arsenic disulfide; red arsenic sulfide; red orpiment
arsenic hemiselenide
arsenic monophosphide
arsenic monoxide
arsenic oxybromide
arsenic oxychloride
Safety Information
Material Safety Data Sheet - ACI Alloys, Inc.
For More Information
American Elements
Chemical & Engineering News
Chemical Elements
ChemGlobe
Chemicool
Environmental Chemistry
Sources
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(3) - Neighbors, Marianne and Tannehill-Jones, Ruth. Human Diseases, 2nd ed.; Thomson Delmar Learning: Clifton Park, NY, 2006; p 32.
(4) - Lide, David R. CRC Handbook of Chemistry and Physics, 83rd ed.; CRC Press: Boca Raton, FL, 2002; p 4:132.
(5) - Lide, David R. CRC Handbook of Chemistry and Physics, 84th ed.; CRC Press: Boca Raton, FL, 2002; p 4:39-4:96.
(6) - Dean, John A. Lange's Handbook of Chemistry, 11th ed.; McGraw-Hill Book Company: New York, NY, 1973; p 4:8-4:149.
(7) - Lide, David R. CRC Handbook of Chemistry and Physics, 84th ed.; CRC Press: Boca Raton, FL, 2002; p 10:147-10:148.
(8) - Speight, James. Lange's Handbook of Chemistry, 16th ed.; McGraw-Hill Professional: Boston, MA, 2004; p 1:132.
(9) - Lide, David R. CRC Handbook of Chemistry and Physics, 83rd ed.; CRC Press: Boca Raton, FL, 2002; p 10:178 - 10:180.
(10) - Lide, David R. CRC Handbook of Chemistry and Physics, 83rd ed.; CRC Press: Boca Raton, FL, 2002; p 4:133.
(11) - Lide, David R. CRC Handbook of Chemistry and Physics, 83rd ed.; CRC Press: Boca Raton, FL, 2002; pp 6:193, 12:219-220.
(12) - Lide, David R. CRC Handbook of Chemistry and Physics, 83rd ed.; CRC Press: Boca Raton, FL, 2002; pp 6:123-6:137.
(13) - Lide, David R. CRC Handbook of Chemistry and Physics, 83rd ed.; CRC Press: Boca Raton, FL, 2002; pp 6:107-6:122.
(14) - Dean, John A. Lange's Handbook of Chemistry, 12th ed.; McGraw-Hill Book Company: New York, NY, 1979; p 9:4-9:94.
(15) - Atomic Mass Data Center. http://amdc.in2p3.fr/web/nubase_en.html (accessed July 14, 2009).
(16) - Halka, Monica and Nordstrom, Brian. Metals & Metalloids; Infobase Publishing: New York, NY, 2011; pg. 97.
(17) - Atkins, Jones, and Laverman. Chemical Principles 6th ed.; W.H. Freeman and Company: New York, NY, 2013; p F94.
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(19) - Lide, David R. CRC Handbook of Chemistry and Physics, 83rd ed.; CRC Press: Boca Raton, FL, 2002; p 14:17.
(20) - Morgan, John W. and Anders, Edward, Proc. Natl. Acad. Sci. USA 77, 6973-6977 (1980)
(21) - Brownlow, Arthur. Geochemistry; Prentice-Hall, Inc.: Englewood Cliffs, NJ, 1979, pp 15-16.