== Notes regarding rework == 

 I've followed WP:SECONDARY regarding the pKa values. However, somewhat oddly I can't find any primary research which backs them up.There's some evidence that it might originate from: Chaudhuri, B. K., and H. G. Mukherjee. "REVIEW ON PERIODIC ACIDS AND PERIODATES (SIMPLE AND COMPLEX)." JOURNAL OF THE INDIAN CHEMICAL SOCIETY 56.11 (1979): 1098-1107. but like anything old from the Indian chemical society it's uterly unobtainable Instead primary  literature gives a different pKa range, shown below. I don't know why the two pKa ranges are so different but I thought I'd note it here. 
 
 :H5IO6 ↔ H4IO6− + H+, pKa = 1.64 

 :H4IO6− ↔ H3IO62− + H+, pKa = 8.36 

 :H3IO62− ↔ H2IO63− + H+, pKa = 14.98 

 With regards to metaperiodic acid (HIO4), I can't find a pKa value anywhere, presumably an accurate pKa can't be determined as it hydrates too rapidly in solution.