What is the primary characteristic of an ionic bond?

Ionic bonding is primarily characterized by the transfer of electrons between atoms. In this type of bond, one atom, typically a metal, donates one or more electrons to another atom, usually a nonmetal. This transfer results in the formation of charged ions: the metal becomes a positively charged ion (cation), and the nonmetal becomes a negatively charged ion (anion). The electrostatic attraction between these oppositely charged ions forms a strong ionic bond.

The other options incorrectly describe different types of bonds or scenarios. The sharing of electrons mentioned in the first choice pertains to covalent bonding, not ionic bonding. The third option suggests that ionic bonds only form between two nonmetals, which doesn't align with the typical formation of ionic bonds, as they usually occur between metals and nonmetals. Lastly, the occurrence of ionic bonds is not limited to organic compounds; they can form in many types of compounds, including inorganic ones. Thus, the transfer of electrons is the essential mechanism that defines ionic bonds clearly.