The correct order of decreasing bond lengths of `CO,CO_(2) and CO_(3)^(2-)` is

Options

A. `Igt IIIgt II`
B. `Igt II gt III`
C. `IIIgt II gtI`
D. `II gt III gt I`

Explanation

(i) Bond length `prop (1)/("Bond order")`
(ii) Bond order is calculated either by `MO` theory or by resonance
(I) `BO` of `CO` as calculated by `MOT =3`
(II) `BO` in `CO_(3)^(2-)` (by resonance method) `= (4)/(3) = 1.33`
(III) `BO` of `CO_(2) = ("No .of bonds in all possible sides")/("No. of resonating structures")`
` = (4)/(2) =2`
`:. BO` of `CO gt CO_(2) gt CO_(3)^(2-)`
Hence bond lenght of `C-O` is `CO_(3)^(2-) gt CO_(2) gt CO` (i.eII gt III gt I) .