How do polyatomic ions form ionic bonds?

Polyatomic ions form ionic bonds by gaining or losing electrons to achieve a stable electron configuration.

Polyatomic ions are ions that consist of two or more atoms covalently bonded together, carrying a net charge. These ions can either be positively charged (cations) or negatively charged (anions). The formation of ionic bonds involving polyatomic ions is similar to that of monatomic ions, which involves the transfer of electrons to achieve a stable electron configuration.

In an ionic bond, one atom donates one or more electrons and becomes a positively charged ion, while the other atom accepts one or more electrons and becomes a negatively charged ion. This transfer of electrons allows both atoms to achieve a stable electron configuration, similar to that of the nearest noble gas. The resulting positive and negative ions are then attracted to each other due to their opposite charges, forming an ionic bond.

For example, consider the formation of calcium carbonate (CaCO3). Calcium (Ca) is a metal that tends to lose two electrons to achieve a stable electron configuration, forming a Ca2+ ion. The carbonate ion (CO3) is a polyatomic ion that has a charge of 2-, meaning it has gained two electrons. When calcium and carbonate ions come together, the calcium ion donates its two electrons to the carbonate ion. This results in both ions achieving a stable electron configuration, and the electrostatic attraction between the Ca2+ and CO3 2- ions forms the ionic bond in calcium carbonate.

In summary, polyatomic ions form ionic bonds by gaining or losing electrons to achieve a stable electron configuration, similar to monatomic ions. The resulting positive and negative ions are then attracted to each other due to their opposite charges, forming an ionic bond.