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The iodate anion, IO3
Space-filling model of the iodate anion

An iodate is a conjugate base of iodic acid.[1] In the iodate anion, iodine is bonded to three oxygen atoms and the molecular formula is IO3. The molecular geometry of iodate is trigonal pyramidal.

Iodate can be obtained by reducing periodate with a thioether. The byproduct of the reaction is a sulfoxide.[2]

Iodates are a class of chemical compounds containing this group. Examples are sodium iodate (NaIO3), silver iodate (AgIO3), and calcium iodate (Ca(IO3)2). iodates resemble chlorates with iodine instead of chlorine.

In acid conditions, iodic acid is formed. Potassium hydrogen iodate (KH(IO3)2) is a double salt of potassium iodate and iodic acid and an acid as well. Iodates are used in the iodine clock reaction.

Potassium iodate, like potassium iodide, has been issued as a prophylaxis against radioiodine absorption in some countries.[3][4]

Other oxyanions[edit]

Iodine can assume oxidation states of −1, +1, +3, +5, or +7. A number of neutral iodine oxides are also known.

Iodine oxidation state −1 +1 +3 +5 +7
Name iodide hypoiodite iodite iodate periodate
Formula I IO IO2 IO3 IO4 or IO65−


  1. ^ Merriam-Webster definition
  2. ^ Qiu, Chao; Sheng Han; Xingguo Cheng; and Tianhui Ren (2005). "Distribution of Thioethers in Hydrotreated Transformer Base Oil by Oxidation and ICP-AES Analysis" (abstract). Industrial & Engineering Chemistry Research 44 (11): 4151–4155. doi:10.1021/ie048833b. Retrieved 2007-05-03. "Thioethers can be oxidized to sulfoxides by periodate, and periodate is reduced to iodate" 
  3. ^
  4. ^