Atomic number:53
Group numbers:17
Period:5
Electronic configuration:[Kr] 4d10 5s2 5p5
Formal oxidation number:-1 +1 +5 +7
Electronegativities:2.66
Atomic radius / pm:133.1
Relative atomic mass:126.90447 ± 0.00003
Iodine was discovered by Bernard Courtois (FR) in 1811. The origin of the name comes from the Greek word iodes meaning violet. It is a shiny, black, non-metallic solid with characteristic odour. It sublimes easily and as a gas it is violet and intensely irritating to the eyes, nose and throat. Iodine occurs on land and in the sea in sodium and potassium compounds. It is required in small amounts by humans. Iodine was once used as an antiseptic, but no longer due to its poisonous nature.
Crystal structure:
base-centered orthorhombic
Unit-cell dimensions / pm:
a=726.47, b=478.57, c=979.08
Space group:
Cmca
Density / g dm-3:4930 (293 K)
Molar volume / cm3mol-1:25.74 (293 K)
Electrical resistivity / μΩcm:1.3E+15 (20 °C)
Thermal conductivity / W m-1K-1:0.449
Melting point / °C:113.7
Boiling point / °C:184.4
Heat of fusion / kJ mol-1:15.27
Heat of vaporization / kJ mol-1:41.67
Heat of atomization / kJ mol-1:107.24
1st ionization energy / kJ mol-1:1008.40
2nd ionization energy / kJ mol-1:1845.90
3rd ionization energy / kJ mol-1:3184.04
in the atmosphere / ppm:-
in the Earth's crust / ppm:0.5
in the oceans / ppm:0.05
2I-+0.535 2I-+0.615 2I3-+0.789 3I-+0.536 IO3- + 3H2O+1.601 IO3- + 2H2O+1.898 HIO + 4H2O+1.389 I2(s) + 10H2O+1.384 I3- + 15H2O+1.357 I- + 5H2O+1.288 HIO3 + H2O+1.626 IO3- + H2O+1.653 HIO + 3H2O+1.290 HIO + 3H2O+1.235 I2(s) + 8H2O+1.300 I3- + 12H2O+1.276 I- + 4H2O+1.215 I+ + 3H2O+1.155 IO- + 2H2O+0.972 I2(s) + 6H2O+1.196 I2(aq) + 6H2O+1.178 ICl2- + 3H2O+1.24 I2(s) + 6H2O+1.169 I3- + 9H2O+1.145 I- + 3H2O+1.078 I2(s) + 2H2O+1.354 I2(s) + 2H2O+2.005 I3- + 3H2O+1.213 I3- + 3H2O+1.701 I- + H2O+1.313 I- + H2O+0.987 I2(s) + 6Cl-+1.28 I2(s) + 2Cl-+1.22 I2(s) + 2Cl-+1.19 I2(s) + 4Cl-+1.056 I2(s) + 2Br-+1.02
52 Tellurium <= 53 Iodine => 54 Xenon