Draw the important resonance forms for the following...

Draw the important resonance forms for the following molecules and ions. (a) $\mathrm{CO}_{3}^{2-}$ (b) $\mathrm{NO}_{3}^{-}$ (c) $\mathrm{NO}_{2}^{-}$ (d) $\mathrm{H}_{2} \mathrm{C}=\mathrm{CH}-\mathrm{CH}_{2}^{+}$ (e) $\mathrm{H}_{2} \mathrm{C}=\mathrm{CH}-\mathrm{CH}_{2}^{-}$ (f) $\mathrm{SO}_{4}^{2-}$ (g) $\left[\mathrm{CH}_{3} \mathrm{C}\left(\mathrm{OCH}_{3}\right)_{2}\right]^{+}$ (h) $\mathrm{B}(\mathrm{OH})_{3}$

Draw the important resonance forms for the following molecules and ions.
(a) $\mathrm{CO}_{3}^{2-}$
(b) $\mathrm{NO}_{3}^{-}$
(c) $\mathrm{NO}_{2}^{-}$
(d) $\mathrm{H}_{2} \mathrm{C}=\mathrm{CH}-\mathrm{CH}_{2}^{+}$
(e) $\mathrm{H}_{2} \mathrm{C}=\mathrm{CH}-\mathrm{CH}_{2}^{-}$
(f) $\mathrm{SO}_{4}^{2-}$
(g) $\left[\mathrm{CH}_{3} \mathrm{C}\left(\mathrm{OCH}_{3}\right)_{2}\right]^{+}$
(h) $\mathrm{B}(\mathrm{OH})_{3}$

Key Concepts

Resonance Structures

Resonance structures are multiple valid Lewis structures that collectively represent the electron distribution in a molecule or ion. They illustrate how electrons are delocalized over two or more atoms rather than confined to a single bond or location, providing a more complete depiction of the molecule’s electronic structure and stability.

Lewis Structures

Lewis structures are diagrams that show the arrangement of valence electrons among atoms in a molecule or ion, including both bonding pairs and lone pairs. They serve as the foundation for understanding more complex phenomena such as resonance by first laying out the connectivity and electron count of each atom.

Formal Charge

Formal charge is calculated for each atom on a Lewis structure to determine the distribution of electrical charge within a molecule or ion. By comparing the number of electrons an atom 'owns' in a structure versus its neutral state, chemists can assess the likelihood and relative stability of various resonance forms.

Electron Delocalization

Electron delocalization refers to the spreading of electrons, particularly pi electrons and lone pairs, over multiple atoms rather than being localized between two atoms. This concept is central to understanding resonance as it explains the stabilization that results from distributing charge over a larger framework.

Charge Distribution and Stability

The distribution of charge across a molecule or ion, especially in resonance forms, is key to its stability. Structures where negative charges reside on more electronegative atoms, and overall minimal charge separation is achieved, are generally favored, highlighting the interplay between charge distribution and the overall energy of the species.

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