ARSENIC

Introduction

Atomic Number: 33
Group: 15 or V A
Atomic Weight: 74.9216
Period: 4
CAS Number: 7440-38-2

Classification

Chalcogen
Halogen
Noble Gas
Lanthanoid
Actinoid
Rare Earth Element
Platinum Group Metal
Transuranium
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
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

Electron Configuration: [Ar] 4s2 3d10 4p3
Block: p
Highest Occupied Energy Level: 4
Valence Electrons: 5

Quantum Numbers:

n = 4
ℓ = 1
m = 1
ms = +½

Bonding

Electronegativity (Pauling scale):6 2.18
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

Specific Heat: 0.329 J/g°C 10 = 24.649 J/mol°C = 0.079 cal/g°C = 5.891 cal/mol°C
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

Abundance

Earth - Source Compounds: sulfides 16
Earth - Seawater: 0.0037 mg/L 17
Earth -  Crust:  1.8 mg/kg = 0.00018% 17
Earth -  Total:  3.2 ppm 18
Mercury -  Total:  6.4 ppm 18
Venus -  Total:  3.1 ppm 18
Chondrites - Total: 4.6 (relative to 106 atoms of Si) 19

Compounds

Safety Information


Material Safety Data Sheet - ACI Alloys, Inc.

For More Information

External Links:

Sources

(1) - Lide, David R. CRC Handbook of Chemistry and Physics, 83rd ed.; CRC Press: Boca Raton, FL, 2002; p 4:4.
(2) - Whitten, Kenneth W., Davis, Raymond E., and Peck, M. Larry. General Chemistry 6th ed.; Saunders College Publishing: Orlando, FL, 2000; p 926.
(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) - T < 1465.24647375309
(17) - Silberberg, Martin S. Chemistry: The Molecular Nature of Matter and Change, 4th ed.; McGraw-Hill Higher Education: Boston, MA, 2006, p 965.
(18) - Lide, David R. CRC Handbook of Chemistry and Physics, 83rd ed.; CRC Press: Boca Raton, FL, 2002; p 14:17.
(19) - Morgan, John W. and Anders, Edward, Proc. Natl. Acad. Sci. USA 77, 6973-6977 (1980)
(20) - Brownlow, Arthur. Geochemistry; Prentice-Hall, Inc.: Englewood Cliffs, NJ, 1979, pp 15-16.