The oxide ion is \(\mathrm{O}^{2-}\). How does this ion differ from the peroxide ion, \(\mathrm{O}_{2}^{2-} ?\) Draw dot diagrams for both.

The electron configuration for a neutral oxygen atom is 1s² 2s² 2p⁴. To form the oxide ion (O²⁻), it gains two electrons to fill its outer shell, giving a total of 10 electrons. So, the electron configuration for \(\mathrm{O}^{2-}\) is 1s² 2s² 2p⁶. On the other hand, the peroxide ion is formed by two oxygen atoms sharing two electrons to create a single bond between them (O-O). Each oxygen atom also gains one more electron, which brings the total number of electrons in the peroxide ion to 12 (6 for each oxygen atom). The electron configuration for \(\mathrm{O}_{2}^{2-}\) is the same as that of \(\mathrm{O}^{2-}\) for each oxygen atom, which is 1s² 2s² 2p⁶.

In this step, we'll draw the Lewis dot diagrams for both ions. For the oxide ion: 1. Write the oxygen symbol (O) and surround it with eight dots, representing the eight valence electrons. 2. Since it's a negatively charged ion, add brackets around the ion and put the charge on the upper right corner. The Lewis dot diagram for the oxide ion (O²⁻) will look like this: \[ [\underset{.}{\overset{.}{O}}\: :]^{2-} \] For the peroxide ion: 1. Write two oxygen symbols (O) with two dots between them, representing the single bond formed by the shared electrons. 2. Add six more dots around each oxygen atom, making sure each oxygen atom has eight electrons in total. 3. As before, add brackets around the ion and put the charge on the upper right corner. The Lewis dot diagram for the peroxide ion (O₂²⁻) will look like this: \[ [ \underset{.}{\overset{.}{O}} - \underset{.}{\overset{.}{O}} :]^{2-} \]

Now that we have the Lewis dot diagrams for both ions, we can compare them and identify their differences: 1. The oxide ion (O²⁻) consists of a single oxygen atom with a charge of 2-, while the peroxide ion (O₂²⁻) consists of two oxygen atoms with a total charge of 2-. 2. The oxide ion has a full octet of electrons around the oxygen atom, while in the peroxide ion, each oxygen atom shares two electrons for a single bond in addition to having six nonbonding valence electrons. In conclusion, the peroxide ion (O₂²⁻) differs from the oxide ion (O²⁻) in having two oxygen atoms linked by a single bond, with each oxygen atom carrying a partial negative charge.