Periodic Table/Iodine
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53I126.9045 Da

Iodine

Halogen·Period 5, Group 17·p-block

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.

Gallery

Iodine Sample

Benjah-bmm27, Public domain, via Wikimedia Commons

Bohr model of Iodine

Physical Propertiesmass · density · phase · crystal

Atomic Mass

126.9045Da

Density

4.9330g/cm³

Phase (STP)

Solid

Melting Point

386.8K

Boiling Point

457.5K

Molar Heat

0.2140J/(mol·K)

Crystal Structure

ORC

Lattice Constant

7.720Å

Atomic Radiiatomic · covalent · van der Waals

Atomic (Empirical)

140.00pm

Covalent

133.00pm

Van der Waals

198.00pm

Electronic Propertieselectronegativity · ionization · affinity

Electron Configuration

[Kr] 4d10 5s2 5p5

Electron Shells

2, 8, 18, 18, 7

Electronegativity

2.66Pauling

Electron Affinity

3.1kJ/mol

1st Ionization Energy

10.5kJ/mol

Oxidation States

-1, +1, +3, +5, +7

Orbital DiagramAufbau · Hund's rule · Pauli exclusion

↑↓
1s2
↑↓
2s2
↑↓
↑↓
↑↓
2p6
↑↓
3s2
↑↓
↑↓
↑↓
3p6
↑↓
↑↓
↑↓
↑↓
↑↓
3d10
↑↓
4s2
↑↓
↑↓
↑↓
4p6
↑↓
↑↓
↑↓
↑↓
↑↓
4d10
↑↓
5s2
↑↓
↑↓
↑
5p5

Full: 1s2 2s2 2p6 3s2 3p6 3d10 4s2 4p6 4d10 5s2 5p5Short: [Kr] 4d10 5s2 5p5

Ionization Energies (53 known)

1st10.5 kJ/mol2nd19.1 kJ/mol3rd29.6 kJ/mol4th40.4 kJ/mol5th51.5 kJ/mol6th74.4 kJ/mol7th87.6 kJ/mol8th150.8 kJ/mol9th171.0 kJ/mol10th197.0 kJ/mol11th220.9 kJ/mol12th247.0 kJ/mol13th279.0 kJ/mol14th307.0 kJ/mol15th335.0 kJ/mol16th365.0 kJ/mol17th393.0 kJ/mol18th505.0 kJ/mol19th535.0 kJ/mol20th569.0 kJ/mol21th601.0 kJ/mol22th649.0 kJ/mol23th683.0 kJ/mol24th762.0 kJ/mol25th800.8 kJ/mol26th1397.0 kJ/mol27th1472.0 kJ/mol28th1553.0 kJ/mol29th1639.0 kJ/mol30th1720.0 kJ/mol31th1812.0 kJ/mol32th1911.0 kJ/mol33th1999.0 kJ/mol34th2093.0 kJ/mol35th2181.0 kJ/mol36th2431.0 kJ/mol37th2510.0 kJ/mol38th2598.0 kJ/mol39th2680.0 kJ/mol40th2836.0 kJ/mol41th2926.0 kJ/mol42th3096.0 kJ/mol43th3185.5 kJ/mol44th7337.0 kJ/mol45th7563.0 kJ/mol46th7811.0 kJ/mol47th8044.0 kJ/mol48th8601.0 kJ/mol49th8867.0 kJ/mol50th9196.0 kJ/mol51th9421.1 kJ/mol52th38717.0 kJ/mol53th39721.5 kJ/molSuccessive Ionization Energies

Emission Spectrumvisible range · characteristic spectral lines

547
512
516
612
I emission
380nm750nm
546.5 nm(100%)511.9 nm(40%)516.1 nm(35%)612.3 nm(20%)

Abundanceby mass

🌍Earth's Crust
450.0 ppb
🌊Ocean
60.0 ppb
✨Universe
1.0 ppb
🧬Human Body
200.0 ppb

Log scale · ppm = parts per million by mass

Biological Role

Essential (trace)

Essential component of thyroid hormones (T₃, T₄). Deficiency causes goiter and cretinism.

Discovery

Discovered By

Bernard Courtois

Named By

—

Year

1811

Nuclear Data

Known Isotopes

42

Stable Isotopes

2

Stable Mass Numbers

106, 127

Natural isotopic abundance (IUPAC recommended values)

Isotopes of I42 known

NuclideZNMass (AMU)Half-lifeDecayJπAbundance
106Istable5353105.953516Stableα——
107I5354106.946935Unknownα5/2+—
108I5355107.94334826.4 msα (0.995%), p (0.005%), β⁺, β⁺p1+—
127Istable5374126.904473Stablestable (1%)5/2+10000.0000%
145I5392144.95584589.7 msβ⁻ (1%), β⁻n, 2n7/2+—
146I5393145.96184694.0 msβ⁻ (1%), β⁻n, 2n——
147I5394146.966505Unknownβ⁻, β⁻n, 2n3/2-—

Click any isotope for its full page with decay chain:

106I107I108I109I110I111I112I113I114I115I116I117I118I119I120I121I122I123I124I125I126I127I128I129I130I131I132I133I134I135I136I137I138I139I140I141I142I143I144I145I146I147I
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