Iodine

Iodine, 53I
Iodine
Pronunciation/ˈədn, -dɪn, -dn/ (EYE-ə-dyne, -⁠din, -⁠deen)
Appearancelustrous metallic gray solid, black/violet liquid, violet gas
Standard atomic weight Ar°(I)
Iodine in the periodic table
Hydrogen Helium
Lithium Beryllium Boron Carbon Nitrogen Oxygen Fluorine Neon
Sodium Magnesium Aluminium Silicon Phosphorus Sulfur Chlorine Argon
Potassium Calcium Scandium Titanium Vanadium Chromium Manganese Iron Cobalt Nickel Copper Zinc Gallium Germanium Arsenic Selenium Bromine Krypton
Rubidium Strontium Yttrium Zirconium Niobium Molybdenum Technetium Ruthenium Rhodium Palladium Silver Cadmium Indium Tin Antimony Tellurium Iodine Xenon
Caesium Barium Lanthanum Cerium Praseodymium Neodymium Promethium Samarium Europium Gadolinium Terbium Dysprosium Holmium Erbium Thulium Ytterbium Lutetium Hafnium Tantalum Tungsten Rhenium Osmium Iridium Platinum Gold Mercury (element) Thallium Lead Bismuth Polonium Astatine Radon
Francium Radium Actinium Thorium Protactinium Uranium Neptunium Plutonium Americium Curium Berkelium Californium Einsteinium Fermium Mendelevium Nobelium Lawrencium Rutherfordium Dubnium Seaborgium Bohrium Hassium Meitnerium Darmstadtium Roentgenium Copernicium Nihonium Flerovium Moscovium Livermorium Tennessine Oganesson
Br

I

At
telluriumiodinexenon
Atomic number (Z)53
Groupgroup 17 (halogens)
Periodperiod 5
Block  p-block
Electron configuration[Kr] 4d10 5s2 5p5
Electrons per shell2, 8, 18, 18, 7
Physical properties
Phase at STPsolid
Melting point(I2) 386.85 K ​(113.7 °C, ​236.66 °F)
Boiling point(I2) 457.4 K ​(184.3 °C, ​363.7 °F)
Density (at 20° C)4.944 g/cm3[3]
Triple point386.65 K, ​12.1 kPa
Critical point819 K, 11.7 MPa
Heat of fusion(I2) 15.52 kJ/mol
Heat of vaporisation(I2) 41.57 kJ/mol
Molar heat capacity(I2) 54.44 J/(mol·K)
Vapour pressure (rhombic)
P (Pa) 1 10 100 1 k 10 k 100 k
at T (K) 260 282 309 342 381 457
Atomic properties
Oxidation states−1, 0, +1, +2,[4] +3, +4, +5, +6, +7 (a strongly acidic oxide)
ElectronegativityPauling scale: 2.66
Ionisation energies
  • 1st: 1008.4 kJ/mol
  • 2nd: 1845.9 kJ/mol
  • 3rd: 3180 kJ/mol
Atomic radiusempirical: 140 pm
Covalent radius139±3 pm
Van der Waals radius198 pm
Color lines in a spectral range
Spectral lines of iodine
Other properties
Natural occurrenceprimordial
Crystal structurebase-centered orthorhombic (oS8)
Lattice constants
Base-centered orthorhombic crystal structure for iodine
a = 725.79 pm
b = 478.28 pm
c = 982.38 pm (at 20 °C)[3]
Thermal expansion74.9×10−6/K (at 20 °C)[a]
Thermal conductivity0.449 W/(m⋅K)
Electrical resistivity1.3×107 Ω⋅m (at 0 °C)
Magnetic orderingdiamagnetic[5]
Molar magnetic susceptibility−88.7×10−6 cm3/mol (298 K)[6]
Bulk modulus7.7 GPa
CAS Number7553-56-2
History
Discovery and first isolationBernard Courtois (1811)
Isotopes of iodine
Main isotopes Decay
abun­dance half-life (t1/2) mode pro­duct
123I synth 13 h β+100% 123Te
124I synth 4.176 d ε 124Te
125I synth 59.40 d ε 125Te
127I 100% stable
129I trace 1.57×107 y β 129Xe
131I synth 8.02070 d β100% 131Xe
135I synth 6.57 h β 135Xe
 Category: Iodine
| references

Iodine is a chemical element; it has symbol I and atomic number 53. The heaviest of the stable halogens, it exists at standard conditions as a semi-lustrous, non-metallic solid that melts to form a deep violet liquid at 114 °C (237 °F), and boils to a violet gas at 184 °C (363 °F). The element was discovered by the French chemist Bernard Courtois in 1811 and was named two years later by Joseph Louis Gay-Lussac, after the Ancient Greek Ιώδης, meaning 'violet'.

Iodine occurs in many oxidation states, including iodide (I), iodate (IO
3
), and the various periodate anions. It is the least abundant of the stable halogens, being the 64th most abundant element. As the heaviest essential mineral nutrient, iodine is required for the synthesis of thyroid hormones.[7] Iodine deficiency affects about two billion people and is the leading preventable cause of intellectual disabilities.[8]

The dominant producers of iodine today are Chile and Japan. Due to its high atomic number and ease of attachment to organic compounds, it has also found favour as a non-toxic radiocontrast material. Because of the specificity of its uptake by the human body, radioactive isotopes of iodine can also be used to treat thyroid cancer. Iodine is also used as a catalyst in the industrial production of acetic acid and some polymers.

It is on the World Health Organization's List of Essential Medicines.[9]

  1. ^ "Standard Atomic Weights: Iodine". CIAAW. 1985.
  2. ^ Prohaska T, Irrgeher J, Benefield J, Böhlke JK, Chesson LA, Coplen TB, Ding T, Dunn PJ, Gröning M, Holden NE, Meijer HA (4 May 2022). "Standard atomic weights of the elements 2021 (IUPAC Technical Report)". Pure and Applied Chemistry. doi:10.1515/pac-2019-0603. ISSN 1365-3075.
  3. ^ a b c Arblaster JW (2018). Selected Values of the Crystallographic Properties of Elements. Materials Park, Ohio: ASM International. ISBN 978-1-62708-155-9.
  4. ^ I(II) is known to exist in monoxide (IO); see Nikitin IV (31 August 2008). "Halogen monoxides". Russian Chemical Reviews. 77 (8): 739–749. Bibcode:2008RuCRv..77..739N. doi:10.1070/RC2008v077n08ABEH003788. S2CID 250898175.
  5. ^ Magnetic susceptibility of the elements and inorganic compounds, in Handbook of Chemistry and Physics 81st edition, CRC press.
  6. ^ Weast R (1984). CRC, Handbook of Chemistry and Physics. Boca Raton, Florida: Chemical Rubber Company Publishing. pp. E110. ISBN 0-8493-0464-4.
  7. ^ "Iodine". Micronutrient Information Center, Linus Pauling Institute, Oregon State University, Corvallis. 2015. Archived from the original on 17 April 2015. Retrieved 20 November 2017.
  8. ^ McNeil Jr DG (16 December 2006). "In Raising the World's I.Q., the Secret's in the Salt". The New York Times. Archived from the original on 12 July 2010. Retrieved 21 July 2009.
  9. ^ World Health Organization (2021). World Health Organization model list of essential medicines: 22nd list (2021). Geneva: World Health Organization. hdl:10665/345533. WHO/MHP/HPS/EML/2021.02.


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