Number of resonance structures for  Chlorate ion is/are

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

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

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

Cl-O bond  order….${\mathrm{ClO}}^{-} \left(1\right)<{\mathrm{ClO}}_2^{-}\left(1.5\right) <{\mathrm{ClO}}_2^{-} \left(1.66\right)<{\mathrm{ClO}}_4^{-}\left(1.75\right) ;$

Cl-O bond length….${\mathrm{ClO}}^{-}>{\mathrm{ClO}}_2^{-}>{\mathrm{ClO}}_3^{-}>{\mathrm{ClO}}_4^{-} ;$

Bond angle….${\mathrm{ClO}}^{-}$-no bond angle ; ${\mathrm{ClO}}_3^{-}$- 107⁰ ; ${\mathrm{ClO}}_4^{-}$- 109.5⁰; In ${\mathrm{ClO}}_2^{-}$ - 111⁰….bp-bp repulsions dominate lp-lp repulsions ;

Acidic strength, oxidizing power, bleaching power…..$\mathrm{HClO}>{\mathrm{HClO}}_2>{\mathrm{HClO}}_3>{\mathrm{HClO}}_3 ;$

Basic strength…….${\mathrm{ClO}}^{-}>{\mathrm{ClO}}_2^{-}>{\mathrm{ClO}}_3^{-}>{\mathrm{ClO}}_4^{-} ;$

Stability….$\mathrm{HClO}<{\mathrm{HClO}}_2<{\mathrm{HClO}}_3<{\mathrm{HClO}}_4;$

Note : While counting the sigma bonds in these acids never forget to count a sigma bond between O-H bond ;

Number of bond pairs around central atom = 5
Number of bond pairs around central according to VSPER theory =3
Number of lone pairs around central atom = 1
Orientation of electron pairs around central atom = Tetrahedral(sp³)
Shape of ${\mathrm{ClO}}_3^{-}$ = pyramidal
Cl–O bond order = 5/3 = 1.66
It has three resonance structures.