In strongly basic conditions, the carbonate ion predominates, while in weakly basic conditions, the bicarbonate ion is prevalent.

In aqueous solution, carbonate, bicarbonate, carbon dioxide, and carbonic acid exist together in a dynamic equilibrium. Exceptions include lithium, sodium, potassium, rubidium, caesium, and ammonium carbonates, as well as many uranium carbonates. Most carbonate salts are insoluble in water at standard temperature and pressure, with solubility constants of less than 1 ×10 −8. This process is called calcination, after calx, the Latin name of quicklime or calcium oxide, CaO, which is obtained by roasting limestone in a lime kiln.Ī carbonate salt forms when a positively charged ion, M +, M 2+, or M 3+, associates with the negatively charged oxygen atoms of the ion by forming electrostatic attractions with them, forming an ionic compound:Ģ M + + CO 2− 3 → M 2CO 3 M 2+ + CO 2− 3 → MCO 3 2 M 3+ + 3 CO 2− 3 → M 2(CO 3) 3 Metal carbonates generally decompose on heating, liberating carbon dioxide from the long term carbon cycle to the short term carbon cycle and leaving behind an oxide of the metal. This resonance can be summarized by a model with fractional bonds and delocalized charges: As in the case of the isoelectronic nitrate ion, the symmetry can be achieved by a resonance among three structures: This structure is incompatible with the observed symmetry of the ion, which implies that the three bonds are the same length and that the three oxygen atoms are equivalent. The Lewis structure of the carbonate ion has two (long) single bonds to negative oxygen atoms, and one short double bond to a neutral oxygen atom. It is the conjugate base of the hydrogencarbonate (bicarbonate) ion, HCO − 3, which is the conjugate base of H 2CO 3, carbonic acid. It has a molecular mass of 60.01 g/mol and carries a total formal charge of −2. It consists of one carbon atom surrounded by three oxygen atoms, in a trigonal planar arrangement, with D 3h molecular symmetry. The carbonate ion is the simplest oxocarbon anion. Carbonates are widely used in industry, such as in iron smelting, as a raw material for Portland cement and lime manufacture, in the composition of ceramic glazes, and more.

Sodium carbonate ('soda' or 'natron') and potassium carbonate ('potash') have been used since antiquity for cleaning and preservation, as well as for the manufacture of glass. The most common are calcite or calcium carbonate, CaCO 3, the chief constituent of limestone (as well as the main component of mollusc shells and coral skeletons) dolomite, a calcium-magnesium carbonate CaMg(CO 3) 2 and siderite, or iron(II) carbonate, FeCO 3, an important iron ore. Carbonate minerals are extremely varied and ubiquitous in chemically precipitated sedimentary rock. In geology and mineralogy, the term 'carbonate' can refer both to carbonate minerals and carbonate rock (which is made of chiefly carbonate minerals), and both are dominated by the carbonate ion, CO 2− 3. The term is also used as a verb, to describe carbonation: the process of raising the concentrations of carbonate and bicarbonate ions in water to produce carbonated water and other carbonated beverages – either by the addition of carbon dioxide gas under pressure or by dissolving carbonate or bicarbonate salts into the water. The word carbonate may also refer to a carbonate ester, an organic compound containing the carbonate group O=C(−O−) 2. A carbonate is a salt of carbonic acid (H 2CO 3), characterized by the presence of the carbonate ion, a polyatomic ion with the formula CO 2− 3.

Charge of carbon dioxide