IODINE

Introduction

Atomic Number: 53
Group: 17 or VII A
Atomic Weight: 126.90447
Period: 5
CAS Number: 7553-56-2

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

Discovered by Courtois in 1811. Iodine, a halogen, occurs sparingly in the form of iodides in sea water from which it is assimilatedby seaweeds, in Chilean saltpeter and nitrate-bearing earth, known as caliche in brines from old sea deposits, and in brackish waters from oil and saltwells. Ultrapure iodine can be obtained from the reaction of potassium iodide with copper sulfate. Several other methods of isolating the element areknown. Iodine is a bluish-black, lustrous solid, volatilizing at ordinary temperatures into a blue-violet gas with an irritating odor; it forms compoundswith many elements, but is less active than the other halogens, which displace it from iodides. Iodine exhibits some metallic-like properties. It dissolvesreadily in chloroform, carbon tetrachloride, or carbon disulfide to form beautiful purple solutions. It is only slightly soluble in water. Iodine compoundsare important in organic chemistry and very useful in medicine. Forty two isotopes and isomers are recognized. Only one stable isotope, iodine-127 is foundin nature. The artificial radioisotope iodine-131, with a half-life of 8 days, has been used in treating the thyroid gland. The most common compounds are theiodides of sodium and potassium (KI) and the iodates (KIO3). Lack of iodine is the cause of goiter. Iodides, and thyroxin which contains iodine, areused internally in medicine, and a solution of KI and iodine in alcohol is used for external wounds. Potassium iodide finds use in photography. Thedeep blue color with starch solution is characteristic of the free element. Care should be taken in handling and using iodine, as contact with the skincan cause lesions; iodine vapor is intensely irritating to the eyes and mucous membranes. Elemental iodine costs about 25 to 75¢/g depending on purityand quantity. 1

• "thyroid hormones...Iodine deficiency remains a major cause of mental retardation and infant mortality and morbidity throughout the world - even though iodine was shown to be essential for human health nearly 100 years ago" 2
• "has been used as an antiseptic and germicide in the form of tincture of iodine, a solution in alcohol." 3
• "About half of the iodine produced commercially is used in the preparation of a variety of organic compounds. The rest is used to prepare inorganic iodides. Potassium iodide is added to animal feeds and to salt (iodized salt) to supply iodide ion as a nutrient. Silver iodide (with silver chloride and silver bromide) is used to make photographic film." 4

Physical Properties

Density:5  4.933 g/cm3

* - at 1 atm

Electron Configuration

Electron Configuration: [Kr] 5s2 4d10 5p5
Block: p
Highest Occupied Energy Level: 5
Valence Electrons: 7

Quantum Numbers:

n = 5
ℓ = 1
m = 0
ms = -½

Bonding

Electronegativity (Pauling scale):6 2.66
Electropositivity (Pauling scale): 1.34
Electron Affinity:7 3.059037 eV
Oxidation States: -1,+5,7

Ionization Potential   eV 8  kJ/mol  
1 10.45126    1008.4
Ionization Potential   eV 8  kJ/mol  
2 19.1313    1845.9
Ionization Potential   eV 8  kJ/mol  
3 33    3184.0

Thermochemistry

Specific Heat: 0.145 J/g°C 9 = 18.401 J/mol°C = 0.035 cal/g°C = 4.398 cal/mol°C
Thermal Conductivity: 0.449 (W/m)/K, 27°C 10
Heat of Fusion: 7.824 kJ/mol 11 = 61.7 J/g
Heat of Vaporization: 20.752 kJ/mol 12 = 163.5 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) 0 0 27.757 116.135288 0 0
(g) 14.923 62.437832 62.28 260.57952 4.627 19.359368

Isotopes

Nuclide Mass 14 Half-Life 14 Nuclear Spin 14 Binding Energy
108I 107.94348(39)# 36(6) ms (1)# 886.13 MeV
109I 108.93815(11) 103(5) μs (5/2+) 903.51 MeV
110I 109.93524(33)# 650(20) ms 1+# 911.58 MeV
111I 110.93028(32)# 2.5(2) s (5/2+)# 919.65 MeV
112I 111.92797(23)# 3.42(11) s 937.04 MeV
113I 112.92364(6) 6.6(2) s 5/2+# 945.11 MeV
114I 113.92185(32)# 2.1(2) s 1+ 953.18 MeV
115I 114.91805(3) 1.3(2) min (5/2+)# 970.57 MeV
116I 115.91681(10) 2.91(15) s 1+ 978.64 MeV
117I 116.91365(3) 2.22(4) min (5/2)+ 986.71 MeV
118I 117.913074(21) 13.7(5) min 2- 994.78 MeV
119I 118.91007(3) 19.1(4) min 5/2+ 1,002.86 MeV
120I 119.910048(19) 81.6(2) min 2- 1,010.93 MeV
121I 120.907367(11) 2.12(1) h 5/2+ 1,028.31 MeV
122I 121.907589(6) 3.63(6) min 1+ 1,036.38 MeV
123I 122.905589(4) 13.2235(19) h 5/2+ 1,044.46 MeV
124I 123.9062099(25) 4.1760(3) d 2- 1,052.53 MeV
125I 124.9046302(16) 59.400(10) d 5/2+ 1,060.60 MeV
126I 125.905624(4) 12.93(5) d 2- 1,068.67 MeV
127I 126.904473(4) STABLE 5/2+ 1,076.74 MeV
128I 127.905809(4) 24.99(2) min 1+ 1,084.81 MeV
129I 128.904988(3) 1.57(4)E+7 a 7/2+ 1,092.88 MeV
130I 129.906674(3) 12.36(1) h 5+ 1,100.95 MeV
131I 130.9061246(12) 8.02070(11) d 7/2+ 1,109.03 MeV
132I 131.907997(6) 2.295(13) h 4+ 1,117.10 MeV
133I 132.907797(5) 20.8(1) h 7/2+ 1,125.17 MeV
134I 133.909744(9) 52.5(2) min (4)+ 1,133.24 MeV
135I 134.910048(8) 6.57(2) h 7/2+ 1,132.00 MeV
136I 135.91465(5) 83.4(10) s (1-) 1,140.07 MeV
137I 136.917871(30) 24.13(12) s (7/2+) 1,148.14 MeV
138I 137.92235(9) 6.23(3) s (2-) 1,146.90 MeV
139I 138.92610(3) 2.282(10) s 7/2+# 1,154.97 MeV
140I 139.93100(21)# 860(40) ms (3)(-#) 1,153.72 MeV
141I 140.93503(21)# 430(20) ms 7/2+# 1,161.79 MeV
142I 141.94018(43)# ~200 ms 2-# 1,160.55 MeV
143I 142.94456(43)# 100# ms [>300 ns] 7/2+# 1,168.62 MeV
144I 143.94999(54)# 50# ms [>300 ns] 1-# 1,176.69 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: halide salts and brines 17
Earth - Seawater: 0.06 mg/L 18
Earth -  Crust:  0.45 mg/kg = 0.000045% 18
Earth -  Total:  13.6 ppb 19
Mercury -  Total:  0.16 ppb 19
Venus -  Total:  14.3 ppb 19
Chondrites - Total: 0.051 (relative to 106 atoms of Si) 20
Human Body - Total: 0.00002% 21

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 4:16.
(2) - Whitten, Kenneth W., Davis, Raymond E., and Peck, M. Larry. General Chemistry 6th ed.; Saunders College Publishing: Orlando, FL, 2000; p 926.
(3) - Whitten, Kenneth W., Davis, Raymond E., and Peck, M. Larry. General Chemistry 6th ed.; Saunders College Publishing: Orlando, FL, 2000; p 947.
(4) - Ebbing, Darrell D. General Chemistry 3rd ed.; Houghton Mifflin Company: Boston, MA, 1990; p 585.
(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) - Lide, David R. CRC Handbook of Chemistry and Physics, 83rd ed.; CRC Press: Boca Raton, FL, 2002; p 10:178 - 10:180.
(9) - Lide, David R. CRC Handbook of Chemistry and Physics, 83rd ed.; CRC Press: Boca Raton, FL, 2002; p 4:133.
(10) - Lide, David R. CRC Handbook of Chemistry and Physics, 83rd ed.; CRC Press: Boca Raton, FL, 2002; pp 6:193, 12:219-220.
(11) - Lide, David R. CRC Handbook of Chemistry and Physics, 83rd ed.; CRC Press: Boca Raton, FL, 2002; pp 6:123-6:137.
(12) - Lide, David R. CRC Handbook of Chemistry and Physics, 83rd ed.; CRC Press: Boca Raton, FL, 2002; pp 6:107-6:122.
(13) - Dean, John A. Lange's Handbook of Chemistry, 12th ed.; McGraw-Hill Book Company: New York, NY, 1979; p 9:4-9:94.
(14) - Atomic Mass Data Center. http://amdc.in2p3.fr/web/nubase_en.html (accessed July 14, 2009).
(15) - Ebbing, Darrell D. General Chemistry 3rd ed.; Houghton Mifflin Company: Boston, MA, 1990; p 77.
(16) - Kotz, John C. and Treichel, Paul. Chemistry & Chemical Reactivity 4th ed.; Thomson Brooks/Cole: Belmont, CA, 1999; pp 161, 173.
(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.
(21) - Lide, David R. CRC Handbook of Chemistry and Physics, 83rd ed.; CRC Press: Boca Raton, FL, 2002; p 7:17.