Iodine

Iodine (I)

Dark violet nonmetallic element, belongs to group 17 of the periodic table. Insoluble in water. Required as a trace element for living organisms. One stable isotope, I-127 exists, in addition to fourteen radioactive isotopes. Chemically the least reactive of the halogens, and the most electropositive metallic halogen. Discovered in 1812 by Courtois.
Atomic Number53
Atomic Weight126.90447
Mass Number127
Group17
Period5
Blockp
Protons53 p+
Neutrons74 n0
Electrons53 e-
Sample of iodine.jpg Iodine-sample.jpg Iodine powder.JPG Iodine microcrystals.JPG Iodine'.JPG Animated Bohr Model Enhanced Bohr Model Bohr Model Orbital Diagram

Properties

Atomic Radius
140 pm
Atomic Volume
Covalent Radius
133 pm
Metallic Radius
Ionic Radius
220.00000000000003 pm
Crystal Radius
206 pm
Van der Waals radius
198 pm
Density
4.933 g/cm³
Boiling Point
457.5 K
Melting Point
386.7 K
Electrons per shell2, 8, 18, 18, 7
Electronegativity
2.66
Electrophilicity
3.0864889135127 eV/particle
Proton Affinity
608.2 kJ/mol
Electron Affinity
3.0590368 eV/particle
Ionization Potential
10.45126 eV/particle
Heat of Vaporization
41.95 kJ/mol
Heat of Fusion
15.52 kJ/mol
Heat of Formation
106.757 kJ/mol
Molar Heat Capacity
54.43 J/(mol K)
Specific Heat Capacity
0.214 J/(g⋅K)
Thermal Conductivity
Gas Basicity
583.5 kJ/mol
Dipole Polarizability
32.9 a₀
C6 Dispersion Coefficient
385 a₀
Oxidation States-1, 1, 3, 5, 7
Color
Slate Gray
Crystal StructureBase Centered Orthorhombic (ORC)
Lattice Constant
7.72 Å
Bulk Modulus
Electrical Resistivity
Electron Configuration[Kr] 4d10 5s2 5p5
Magnetic Ordering
Magnetic Susceptibility
PhaseSolid
Poisson Ratio
Shear Modulus
Young's Modulus
Allotropes
Alternate Names
Adiabatic Index
Appearance
Electric Conductivity
Critical Pressure
Critical Temperature
Curie Point
Electrical
Hardness
Magnetic Susceptibility
Magnetic
Neel Point
Neutron Cross Section
Neutron Mass Absorption
Gas Phase
Quantum Numbers
Refractive Index
Space Group
Speed of Sound
Superconducting Point
Thermal Expansion
Valence Electrons
Classification
CategoryHalogens, Halogens
CAS GroupVIIB
IUPAC GroupVIIA
Glawe Number99
Mendeleev Number109
Pettifor Number97
Geochemical Classsemi-volatile
Goldschmidt Classlitophile
Radioactivity
RadioactiveNo
Decay Mode
Half-Life
Lifetime
Abundance
Abundance in Earth's crust
0.45 mg/kg
Abundance in Oceans
0.06 mg/L
Abundance in Human Body
Abundance in Meteor
Abundance in Sun
Abundance in Universe1×10-7%

Isotopes of Iodine

Stable Isotopes
127I
Unstable Isotopes
108I 109I 110I 111I 112I 113I 114I 115I 116I 117I 118I 119I 120I 121I 122I 123I 124I 125I 126I 128I 129I 130I 131I 132I 133I 134I 135I 136I 137I 138I 139I 140I 141I 142I 143I 144I

History

Iodine was discovered by French chemist Bernard Courtois in 1811. He treated the liquor obtained from the extraction of kelp, with sulfuric acid to produce a vapour with a violet color. In 1812, Joseph Louis Gay-Lussac demonstrated that iodine was an element and its chemical relationship to chlorine. From the Greek word iodes, violet

DiscoverersBernard Courtois
Discovery LocationFrance
Discovery Year1811
Name OriginGreek: iôeides (violet colored).
Elemental iodine is toxic if taken orally
Kelp was the main source of natural iodine in the 18th and 19th centuries

Uses

Iodine compounds are important in organic chemistry and very useful in medicine. A solution containing potassium iodide and iodine in alcohol is used to disinfect external wounds. Silver iodide is a major ingredient to traditional photographic film. Iodine is added to table salt to prevent thyroid disease. Required in small amounts by humans. Once used as an antiseptic, but no longer due to its poisonous nature.

Sources

Occurs on land and in the sea in sodium and potassium compounds.