All oxo acids of chlorine are monobasic….contain one O-H group/molecule ;

All the pi bonds in these acids or their oxo anions are $\mathrm{d\pi }-\mathrm{p\pi }$ bonds ;

In all oxo acids of chlorine the hybridization of chlorine atom is sp³ ;

Number of bond pairs around central atom = 3
Number of bond pairs around central atom according to VSPER theory = 2 (one single bond and one double bond)
Number of lone pairs around central atom = 2
Orientation of electron pairs around central atom = Tetrahedral(sp³)
Shape of ${\mathrm{ClO}}_2^{-}$= Angular
Cl–O bond order = 3/2 = 1.5
It has two resonance structures.