CO3, or carbonate ion, is a polyatomic ion with the chemical formula CO₃²⁻. It consists of one carbon atom covalently bonded to three oxygen atoms, and it carries a negative two charge. Carbonate is commonly found in nature, often in minerals like calcite and aragonite, and plays a significant role in geological processes. In addition to its natural occurrence, CO3 is important in various chemical reactions, particularly in the formation of carbonates and bicarbonates. It is also a key component in the carbon cycle, contributing to the regulation of pH levels in aquatic systems and influencing the availability of nutrients in ecosystems.