Many of the acids and salts corresponding to the positive oxidation numbers of the halogens are not listed in the catalogue of a major international chemical supplier: 

(a) KClO₄ and KIO₄ are available but KBrO₄ is not, 

(b) KClO₃, KBrO₃, and KIO₃ are all available, 

(c) NaClO₂ and NaBrO₂⋅3H₂O are available but salts of IO₂⁻ are not, 

(d) Only ClO⁻ salts are available but the bromine and iodine analogues are not. Describe the probable reason for the unavailability of those salts of the oxoanions.