Which oxidation states can iodine have in its compounds?

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Iodine exhibits a variety of oxidation states in its chemical compounds. In addition to the negative oxidation state found in iodides, iodine forms numerous compounds featuring positive oxidation states, specifically +1, +3, +5, and +7.1

These states are characterized by the following:

+1: Found in compounds such as iodine bromide.1
+3: Observed in various iodine compounds.1
+5: Exhibited in iodates, such as the moderately strong iodic acid ( $H I O_{3}$ ) and iodine pentoxide ( $I_{2} O_{5}$ ).1
+7: Found in periodates, such as potassium metaperiodate ( $K I O_{4}$ ) and silver paraperiodate ( $A g_{5} I O_{6}$ ).1

The existence of these positive oxidation states is facilitated by the relatively low first ionization potential of the iodine atom compared to lighter halogen atoms. Additionally, the large size of the iodine atom allows it to accommodate a relatively high number of oxygen atoms in its structure, particularly in the case of periodates.1