Explain the important aspects of resonance with reference to the $CO_3^{2-}$ ion.

Explain the structure of $CO_{2}$ molecule.

Which of the following statements is correct about $CO_3^{2-}$ ?
$A$. The hybridisation of the central atom is $sp^3$.
$B$. Its resonance structure has one $C-O$ single bond and two $C=O$ double bonds.
$C$. The average formal charge on each oxygen atom is $0.67$ units.
$D$. All $C-O$ bond lengths are equal.

The correct arrangement of the species in the decreasing order of the bond length between carbon and oxygen in them is

Resonance in $X_2Y$ can be represented as shown in the image. The enthalpy of formation of $X_2Y$ $(X \equiv X(g) + \frac{1}{2} Y = Y(g) \rightarrow X_2Y(g))$ is $80 \ kJ \ mol^{-1}$. The magnitude of resonance energy of $X_2Y$ is $......... \ kJ \ mol^{-1}$ (nearest integer value). Given: Bond energies of $X \equiv X, X=X, Y=Y$ and $X=Y$ are $940, 410, 500$ and $602 \ kJ \ mol^{-1}$ respectively. Valence $X: 3, Y: 2$.

Which of the following cations is more stable?