What are carbonates primarily composed of?

Carbonates are primarily composed of carbon, oxygen, and a metal element. In this context, carbonates refer to a class of chemical compounds that include a carbonate ion (CO₃²⁻) bonded to a metal cation. Common examples of carbonates include calcium carbonate (CaCO₃), magnesium carbonate (MgCO₃), and sodium carbonate (Na₂CO₃).

The structure of carbonates involves the carbonate ion, which consists of one carbon atom centrally located and bonded to three oxygen atoms. The presence of a metal cation alongside the carbonate ion forms a stable ionic compound. Understanding the composition of carbonates is essential for various applications, especially in environmental chemistry, geology, and agriculture, as they play crucial roles in processes such as weathering, soil fertility, and water hardness.

The other options suggest different combinations of elements that do not accurately describe the composition of carbonates and thus do not reflect the correct information on this chemical category.