Introduction
Group: 17 or VII A
Atomic Weight: 126.90447
Period: 5
CAS Number: 7553-56-2
Classification
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
Electron Configuration: [Kr] 5s2 4d10 5p5
n = 5
Electronegativity (Pauling scale):6 2.66
Specific Heat: 0.145 J/g°C 9 = 18.401 J/mol°C = 0.035 cal/g°C = 4.398 cal/mol°C
F2 (g) + 2 NaI (aq) → 2 NaF (aq) + I2 (s)
Earth - Source Compounds: halide salts and brines 17
External Links:
(1) - Lide, David R. CRC Handbook of Chemistry and Physics, 83rd ed.; CRC Press: Boca Raton, FL, 2002; p 4:16.
* - at 1 atm
Electron Configuration
Block: p
Highest Occupied Energy Level: 5
Valence Electrons: 7
Quantum Numbers:
ℓ = 1
mℓ = 0
ms = -½
Bonding
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
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
H2 (g) + 1 I2 (g) → 2 HI (g)
2 NaI (aq) + 1 Cl2 (g) → 2 NaCl (aq) + I2 (aq) 15
Zn (s) + 1 I2 (s) → ZnI2 (s) 16
2 La (s) + 3 I2 (g) → 2 LaI3 (s)
2 Dy (s) + 3 I2 (g) → 2 DyI3 (s)
2 I2 (s) + 5 Cl2 (g) + 6 H2O (ℓ) → 2 HIO3 (aq) + 10 HCl (aq)
Al2(SO4)3 (aq) + KIO3 (aq) + 5 KI (aq)3 H2O (ℓ) → 2 Al(OH)3 (s) + 3 I2 (s) + 3 K2SO4 (aq)
6 HCl (aq) + 4 KI (aq) + K2SeO3 (aq) → 2 I2 (s) + 6 KCl (aq) + Se (s hexagonal black) + 3 H2O (ℓ)
K2Cr2O7 + 6 NaI + 7 H2SO4 → Cr2(SO4)3 + 3 I2 + 3 Na2SO4 + K2SO4
Abundance
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
1-iodopropane; n-propyl iodide
acetyl iodide
aluminum iodide; aluminium iodide
arsenic diiodide
arsenic triiodide
barium iodide
barium iodide dihydrate
barium iodide hexahydrate
berkelium(III) iodide
beryllium iodide
bismuth(III) iodide
bismuth(III) oxyiodide
boron triiodide
cadmium iodide
calcium iodide
californium(II) iodide
californium(III) iodide
cerium(II) iodide
cerium(III) iodide
cesium iodide; caesium iodide
chromium(II) iodide
chromium(III) iodide
chromium(IV) iodide
cobalt(II) iodide
copper(I) iodide; cuprous iodide
curium(III) iodide
cyanogen iodide
disulfur diiodide
dysprosium(II) iodide
dysprosium(III) iodide
einsteinium(II) iodide
einsteinium(III) iodide
erbium(III) iodide
europium(II) iodide
europium(III) iodide
gadolinium(II) iodide
gadolinium(III) iodide
gallium(III) iodide
germanium(II) iodide
germanium(IV) iodide
gold(I) iodide
gold(III) iodide
hafnium iodide
holmium iodide
hydroiodic acid; hydrogen iodide*
indium(I, III) iodide
indium(III) iodide
iodine heptafluoride
iodine monoazide
iodine monochloride
iodine monofluoride
iodine pentafluoride
iodine trichloride
iodine(III) fluoride
iridium(II) iodide
iridium(III) iodide
iridium(IV) iodide
iron(II) iodide; ferrous iodide
iron(III) iodide
lanthanum iodide
lead(II) iodide
lithium iodide
lithium iodide dihydrate
lithium iodide monohydrate
lithium iodide trihydrate
lutetium iodide
magnesium iodide
manganese(II) iodide
manganese(II) iodide tetrahydrate
mercury(I) iodide
mercury(II) iodide
molybdenum(II) iodide
molybdenum(III) iodide
molybdenum(IV) iodide
neodymium(II) iodide
neodymium(III) iodide
neopentyl iodide
neptunium(III) iodide
nickel(II) iodide
niobium(III) iodide
niobium(IV) iodide
niobium(V) iodide
nitrogen triiodide
osmium(I) iodide
osmium(II) iodide
osmium(III) iodide
palladium(II) iodide
phosphorus tetraiodide
phosphorus triiodide
platinum(II) iodide
platinum(III) iodide
platinum(IV) iodide
plutonium(III) iodide
potassium iodide
praseodymium(II) iodide
praseodymium(III) iodide
protactinium(III) iodide
protactinium(IV) iodide
radium iodide
rhenium(III) iodide
rhenium(IV) iodide
rhodium(III) iodide
rubidium iodide
ruthenium(II) iodide
ruthenium(III) iodide
samarium(II) iodide
samarium(III) iodide
scandium(III) iodide
silicon tetraiodide
silver iodide
silver triiodide
sodium iodide
sodium iodide dihydrate
strontium iodide
tantalum(IV) iodide
tantalum(V) iodide
tellurium monoiodide
tellurium tetraiodide
terbium(III) iodide
thallium(I) iodide
thallium(I) triiodide
thorium(II) iodide
thorium(III) iodide
thorium(IV) iodide
thulium(II) iodide
thulium(III) iodide
tin(II) iodide
tin(IV) iodide
titanium(II) iodide
titanium(III) iodide
titanium(IV) iodide
tungsten(II) iodide
tungsten(III) iodide
tungsten(IV) iodide
tungsten(VI) dioxydiiodide
uranium(III) iodide
uranium(IV) iodide
vanadium(II) iodide
vanadium(III) iodide
vanadium(IV) iodide
ytterbium(II) iodide
ytterbium(III) iodide
yttrium(III) iodide
zinc iodide
zirconium(II) iodide
zirconium(III) iodide
zirconium(IV) iodide
Safety Information
Material Safety Data Sheet - ACI Alloys, Inc.
For More Information
American Elements
Chemical & Engineering News
Chemical Elements
ChemGlobe
Chemicool
Environmental Chemistry
Sources
(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.
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(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.