Karbonaattiioniryhmän

Karbonaattiioniryhmän, scientifically known as the carbonate ion, is a polyatomic anion with the chemical formula CO₃²⁻. It consists of one central carbon atom covalently bonded to three oxygen atoms. The overall charge of the ion is negative two, meaning it carries two excess electrons. This charge is delocalized across the three oxygen atoms due to resonance, making the carbon-oxygen bonds intermediate in character between single and double bonds. The carbonate ion is planar and trigonal planar in geometry.

The carbonate ion is a fundamental component of many minerals, most notably in the form of carbonate rocks such as limestone (calcium carbonate, CaCO₃) and dolomite (calcium magnesium carbonate, CaMg(CO₃)₂). These rocks are abundant in the Earth's crust and play a significant role in geological processes, including weathering and the carbon cycle. In aqueous solutions, carbonate ions can act as both a weak base and a ligand in coordination chemistry. They are formed through the dissolution of carbon dioxide in water, especially in the presence of alkaline substances.

Furthermore, carbonate ions are crucial in biological systems. For instance, they are involved in the formation of shells and skeletons of marine organisms like mollusks and corals, which are primarily composed of calcium carbonate. In human physiology, bicarbonate (HCO₃⁻), a related ion, is essential for buffering blood pH. The presence of carbonate ions is often indicative of certain water chemistry conditions, affecting solubility and reactivity of other dissolved species.