Iodous acid
Iodous acid is the chemical compound with the formula HIO2. Its salts are named iodites; these are exceedingly unstable and have been observed but never isolated. They will rapidly disproportionate to molecular iodine and iodates.
Other oxyacids
Iodous acid is part of a series of oxyacids in which 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 | Hydrogen iodide | Hypoiodous acid | Iodous acid | Iodic acid | Periodic acid |
| Formula | HI | HIO | HIO2 | HIO3 | HIO4 or H5IO6 |