Question: Draw a Lewis structure for each ion.

$$\begin{gathered} \mathbf{a}\mathbf{.}\mathbf{}{\mathbf{CH}}_{\mathbf{3}}{\mathbf{O}}^{\mathbf{-}} \\ \mathbf{b}\mathbf{.}\mathbf{}{{\mathbf{HC}}_{\mathbf{2}}}^{\mathbf{-}} \\ \mathbf{c}\mathbf{.}\mathbf{}{\left({\mathrm{CH}}_3{\mathrm{NH}}_3\right)}^{\mathbf{+}} \\ \mathbf{d}\mathbf{.}\mathbf{}{\left({\mathrm{CH}}_3\mathrm{NH}\right)}^{-} \end{gathered}$$

The Lewis structures are used to show the bonded electrons and lone pairs in a molecule.

The carbon atom has four valence electrons. The oxygen atom has six, and the hydrogen atom has one electron in the valence shell.

a. Eight electrons have been used for the sigma bonding, and the oxygen atom has three lone pairs, due to which it acquires a negative charge.

The given ion is the methoxide ion formed by the loss of a hydrogen ion from the methanol. It is a conjugate base of methanol.

The Lewis dot structure for methoxide ion.

b. There are ten valence electrons, and out of these, nine electrons are involved in the sigma bonding. The remaining electron is on the carbon, and which leads to the attainment of negative charge on carbon atom.

The Lewis dot structure of acetylene anion.

c.In the given ion, there are fifteen valence electrons the different atoms in this molecule have contributed. Due to the positive charge on the nitrogen atom, there are now 14 electrons involved in the bonding

The Lewis structure for methylammonium cation

d. The total number of valence electrons contributed by each atom in this ion is 13. Due to the negative charge on the nitrogen atom, the number of valence electrons becomes 14. In the given structure, the nitrogen atom acquires a negative charge.

The Lewis dot structure of methylammonium anion