Cobalt(II) oxide

Cobalt(II) oxide is an inorganic compound with formula CoO, composed of cobalt ions in the +2 oxidation state and oxide ions. It is a basic, typically green-to-black solid with a rock-salt crystal structure.

Cobalt: Cobalt is a chemical element with atomic number 27, known for hard, magnetic metals and colored compounds. Cobalt supplies the +2 cations in CoO.
Non-stoichiometric compound: A non-stoichiometric compound has elemental proportions that vary from a simple whole-number ratio. Cobalt(II) oxide commonly contains cobalt vacancies and can depart from ideal CoO composition.
Ceramic glaze: A ceramic glaze is a glassy coating fused to a ceramic surface during firing. Cobalt compounds, including CoO, can supply color to glazes.
Cobalt(III) oxide: Cobalt(III) oxide is a cobalt oxide in which cobalt is assigned the +3 oxidation state. It contrasts with CoO in formal cobalt valence and composition.
Oxide: An oxide is a chemical compound in which oxygen is bonded to one or more other elements. Oxide ions balance cobalt’s positive charge in CoO.
Cobalt vacancy: A cobalt vacancy is a missing cobalt atom or ion at a lattice site in a cobalt-containing solid. These defects help produce cobalt-deficient compositions in CoO.
Cobalt blue: Cobalt blue is a vivid blue pigment based on cobalt aluminate, CoAl₂O₄. CoO can serve as a cobalt source when cobalt-containing ceramic pigments are made.
Nickel(II) oxide: Nickel(II) oxide is an inorganic compound with formula NiO and a rock-salt crystal structure. NiO shares CoO’s structure but contains a different transition metal.
Oxidation state: An oxidation state is the formal charge assigned to an atom under a set of electron-allocation rules. The +2 state distinguishes CoO from cobalt oxides with different compositions.
Point defect: A point defect is a localized disruption of a crystal lattice, such as a vacancy or an interstitial atom. Cobalt vacancies are the lattice-scale imperfections central to CoO’s nonstoichiometry.

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