Copper(II) carbonate or cupric carbonate is a

chemical compound A chemical compound is a chemical substance composed of many identical molecules (or molecular entities) containing atoms from more than one chemical element held together by chemical bonds. A molecule consisting of atoms of only one element ...

with formula . At ambient temperatures, it is an ionic solid (a

salt In common usage, salt is a mineral composed primarily of sodium chloride (NaCl). When used in food, especially in granulated form, it is more formally called table salt. In the form of a natural crystalline mineral, salt is also known as r ...

) consisting of

copper Copper is a chemical element; it has symbol Cu (from Latin ) and atomic number 29. It is a soft, malleable, and ductile metal with very high thermal and electrical conductivity. A freshly exposed surface of pure copper has a pinkish-orang ...

(II)

cation An ion () is an atom or molecule with a net electrical charge. The charge of an electron is considered to be negative by convention and this charge is equal and opposite to the charge of a proton, which is considered to be positive by convent ...

s and

carbonate A carbonate is a salt of carbonic acid, (), characterized by the presence of the carbonate ion, a polyatomic ion with the formula . The word "carbonate" may also refer to a carbonate ester, an organic compound containing the carbonate group ...

anion An ion () is an atom or molecule with a net electrical charge. The charge of an electron is considered to be negative by convention and this charge is equal and opposite to the charge of a proton, which is considered to be positive by conven ...

s . This compound is rarely encountered because it is difficult to prepare and readily reacts with water moisture from the air. The terms "copper carbonate", "copper(II) carbonate", and "cupric carbonate" almost always refer (even in chemistry texts) to a

basic copper carbonate Basic copper carbonate is a chemical compound, more properly called copper(II) carbonate hydroxide. It can be classified as a coordination polymer or a salt (chemistry), salt. It consists of copper, copper(II) bonded to carbonate and hydroxide ...

(or copper(II) carbonate

hydroxide Hydroxide is a diatomic anion with chemical formula OH−. It consists of an oxygen and hydrogen atom held together by a single covalent bond, and carries a negative electric charge. It is an important but usually minor constituent of water. It ...

), such as (which occurs naturally as the mineral

malachite Malachite () is a copper Carbonate mineral, carbonate hydroxide mineral, with the chemical formula, formula Basic copper carbonate, Cu2CO3(OH)2. This opaque, green-banded mineral crystallizes in the monoclinic crystal system, and most often for ...

) or (

azurite Azurite or '' Azure spar'Krivovichev V. G.'' Mineralogical glossary. Scientific editor A. G. Bulakh. — St.Petersburg: St.Petersburg Univ. Publ. House. 2009. — 556 p. — ISBN 978-5-288-04863-0. ''(in Russian)'' is a soft, deep-blue copp ...

). For this reason, the qualifier neutral may be used instead of "basic" to refer specifically to .

Preparation

Reactions that may be expected to yield , such as mixing solutions of

copper(II) sulfate Copper(II) sulfate is an inorganic compound with the chemical formula . It forms hydrates , where ''n'' can range from 1 to 7. The pentahydrate (''n'' = 5), a bright blue crystal, is the most commonly encountered hydrate of copper(II) sulfate, whi ...

and

sodium carbonate Sodium carbonate (also known as washing soda, soda ash, sal soda, and soda crystals) is the inorganic compound with the formula and its various hydrates. All forms are white, odourless, water-soluble salts that yield alkaline solutions in water ...

in ambient conditions, yield instead a basic carbonate and , due to the great affinity of the ion for the

anion . Thermal decomposition of the basic carbonate at atmospheric pressure yields

copper(II) oxide Copper(II) oxide or cupric oxide is an inorganic compound with the formula CuO. A black solid, it is one of the two stable oxides of copper, the other being Cu2O or copper(I) oxide (cuprous oxide). As a mineral, it is known as tenorite, or so ...

rather than the carbonate. In 1960, C. W. F. T. Pistorius claimed synthesis by heating basic copper carbonate at in an atmosphere of

carbon dioxide Carbon dioxide is a chemical compound with the chemical formula . It is made up of molecules that each have one carbon atom covalent bond, covalently double bonded to two oxygen atoms. It is found in a gas state at room temperature and at norma ...

at and water at for 36 hours. The bulk of the products was well-crystallized malachite , but a small yield of a rhombohedral substance was also obtained, claimed to be . However, this synthesis was apparently not reproduced. Reliable synthesis of true copper(II) carbonate was reported for the first time in 1973 by Hartmut Ehrhardt et al. The compound was obtained as a gray powder, by heating basic copper carbonate in an atmosphere of carbon dioxide (produced by the decomposition of silver oxalate, ) at and . The compound was determined to have a

monoclinic In crystallography, the monoclinic crystal system is one of the seven crystal systems. A crystal system is described by three Vector (geometric), vectors. In the monoclinic system, the crystal is described by vectors of unequal lengths, as in t ...

structure.

Chemical and physical properties

The stability of dry depends critically on the partial pressure of carbon dioxide (). It is stable for months in dry air, but decomposes slowly into and if is less than . In the presence of water or moist air at , is stable only for above and pH between about 4 and 8. Below that partial pressure, it reacts with water to form a basic carbonate (

, ). : In highly basic solutions, the complex anion is formed instead. The solubility product of the true copper(II) carbonate was measured by Reiterer and others as pK_so = 11.45 ± 0.10 at .

Structure

In the

crystal structure In crystallography, crystal structure is a description of ordered arrangement of atoms, ions, or molecules in a crystalline material. Ordered structures occur from intrinsic nature of constituent particles to form symmetric patterns that repeat ...

of , copper adopts a distorted square pyramidal coordination environment with

coordination number In chemistry, crystallography, and materials science, the coordination number, also called ligancy, of a central atom in a molecule or crystal is the number of atoms, molecules or ions bonded to it. The ion/molecule/atom surrounding the central ion ...

5. Each carbonate ion bonds to 5 copper centres. File:Copper(II)-carbonate-unit-cell-3D-bs-N17-M25.png,

Unit cell In geometry, biology, mineralogy and solid state physics, a unit cell is a repeating unit formed by the vectors spanning the points of a lattice. Despite its suggestive name, the unit cell (unlike a unit vector In mathematics, a unit vector i ...

of CuCO₃ File:Copper(II)-carbonate-xtal-Cu-coordination-3D-bs-N17-M25.png, Copper coordination environment File:Copper(II)-carbonate-xtal-carbonate-coordination-3D-bs-N17-M25.png, Carbonate coordination environment

References

Rolf Grauer (1999)
Solubility Products of M(II) Carbonates
". Technical Report NTB-99-03, NAGRA - National Cooperative for the Disposal of Radioactive Waste; pages 8, 14, and 17. Translated by U. Berner. {{copper compounds Copper(II) compounds Carbonates