${\left[ {O \leftarrow \mathop {\mathop {Cr}\limits_ \downarrow ^ \uparrow }\limits_O^O - O - \mathop {\mathop {Cr}\limits_ \downarrow ^ \uparrow }\limits_O^O \to O} \right]^{2 - }}$
$6,$ $Cr - O$ bonds are equivalent.
$(I)\, CO^{2-}_3$ $(II)\, XeF_4$ $(III)\, I^-_3$ $(IV)\, NCl_3$ $(V)$ $BeCl_2$