This element was discovered by B. Courtois in Paris in 1811. Its name comes from the Greek iodes (violet).
Ionization energies
II 10.4 eV, III 19.1 eV, IIII 33.2 eV.
No I line is observed in the sun. Ionized iodine was found in one Ap star of the Cr-Eu-Sr subgroup by Jaschek and Brandi (1972).
Isotopes
I occurs in the form of I127. There exist a long-lived isotope,
I129, with a half life of
1.7 × 107 years and 22 short-lived
isotopes and isomers. I129 in principle could be used for
radioactive dating.
Origin
I is an r process element.
Published in "The Behavior of Chemical Elements in Stars", Carlos Jaschek and Mercedes Jaschek, 1995, Cambridge University Press.