The shape of  $\text{C}l{\text{O}}_3^{-}$ is

The structure of  $\text{C}l{\text{O}}_3^{-}$ is shown below.

The atomic number of chlorine, Cl is 17.

It has total 7 electrons of its valency shell. Hence, valency of Cl is 7.

Negative anion means it accept one electron from other species.

$\text{Number\hspace{0.17em}of Hybrid orbitals\hspace{0.17em}=}\frac{7+1}{2}=4;{\text{\hspace{0.17em}\hspace{0.17em}sp}}^{\text{3}}$

Although chlorine ${\text{sp}}^{\text{3}}$ has hybridization in $\text{C}l{\text{O}}_3^{-}$ it has “pyramidal 

geometry”. This is due to lone pair bond pair repulsions acting in  $\text{C}l{\text{O}}_3^{-}$ ion.