Question

Draw Lewis electron dot diagrams for the following species, indicating formal charges and resonance diagrams where applicable.
(a) ${\mathbf{H}}_{\mathbf{3}}{\mathbf{NBF}}_{\mathbf{3}}$

(b) role="math" localid="1663750636269" ${\mathbf{CH}}_{\mathbf{3}}{\mathbf{COO}}^{\mathbf{-}}$(acetate ion)

(c) role="math" localid="1663750655104" ${{\mathbf{HCO}}^{\mathbf{-}}}_{\mathbf{3}}$(hydrogen carbonate ion)

Short answer

The Lewis electron dot diagrams for the following species,

Step-by-step solution

Introduction.

In this exercise, one needs to create various Lewis structures.There could also be some species made of specific atoms with positive and negative charges but without a net charge. Otherwise, charged species may have resonance structures that show an electron delocalization between a number of the atoms.

(a) HNC - hydrogen isocyanide

Two resonance forms of the structure are possible: a bent structure without charges and a linear structure with charges. Also take note of the absence of an octet in the carbon atom. The molecule with a different constitution (HCN) is also present in the second structure.

(b) CH3COO-

The acetate (as all carboxylate) anions have a symmetrical, negatively charged group at the top: this symmetry requires the electron configuration to be delocalized which is represented by the two resonance structures depicted below.
The delocalized $\mathrm{\pi }$system consists of 4 electrons on 3 centers.

(c) HCO-3

The hydrogen carbonate anion has a similar (4 electron 3 center $\mathrm{\pi }$system) structure.
If the other acidic hydrogen (see bottom) would dissociate, then the delocalization would cover the whole particle.