"Ortho"-periodic acid can lose all its protons, eventually forming the periodate ion [IO4]−.It can also be protonated in strongly acidic conditions to give the octahedral ion [I(OH)6]+, completing the isoelectronic series, [E(OH)6]"z", E = Sn, Sb, Te, I; "z" = −2, −1, 0, +1.