The compound calcium carbonate contains the calcium ion (Ca2+) and the polyatomic carbonate ion (CO32-). Explain why calcium carbonate is considered to be an ionic compound when it contains both ionic and covalent bonds.
The Correct Answer and Explanation is:
Calcium carbonate (CaCO₃) is considered an ionic compound despite containing both ionic and covalent bonds due to the nature of the interactions between its ions. The compound is made up of the calcium ion (Ca²⁺) and the carbonate ion (CO₃²⁻).
The key factor that categorizes calcium carbonate as an ionic compound is the type of bonding between the calcium ion and the carbonate ion. Calcium, a metal, loses two electrons to form a positively charged ion (Ca²⁺), which is characteristic of ionic compounds. This Ca²⁺ ion is then attracted to the negatively charged carbonate ion (CO₃²⁻), forming an ionic bond. The attraction between the oppositely charged ions is strong, which is typical of ionic bonding, and results in the formation of an ionic lattice structure in the solid form of calcium carbonate.
On the other hand, within the carbonate ion (CO₃²⁻), the bonding between the carbon atom and the oxygen atoms is covalent. The carbon atom shares electrons with the oxygen atoms to form a trigonal planar structure, where the electrons are not transferred between atoms but shared. This covalent bonding is specific to the carbonate ion itself, but it does not affect the overall ionic nature of calcium carbonate as a whole.
In summary, calcium carbonate is classified as an ionic compound because the overall bonding between Ca²⁺ and CO₃²⁻ is ionic, characterized by the electrostatic attraction between the oppositely charged ions. Even though the carbonate ion contains covalent bonds, the ionic interaction between the calcium and carbonate ions dominates, classifying the compound as ionic.
