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Two crystalline forms are known, both being very similar to the corresponding potassium sulfate. Orthorhombic β-K 2 CrO 4 is the common form, but it converts to an α-form above 666 °C. [1] These structures are complex, although the chromate ion adopts the typical tetrahedral geometry. [2]
2 CrO 2− 4 + 2 H + ⇌ Cr 2 O 2− 7 + H 2 O. The predominance diagram shows that the position of the equilibrium depends on both pH and the analytical concentration of chromium. [notes 1] The chromate ion is the predominant species in alkaline solutions, but dichromate can become the predominant ion in acidic solutions.
The Pourbaix diagram for chromium in pure water, perchloric acid, or sodium hydroxide [1] [2]. Chromium compounds are compounds containing the element chromium (Cr). Chromium is a member of group 6 of the transition metals.
Many solids, e.g. graphite, adopt low-dimensional structures, in which case the layers (2-D) or chains (1-D) should be shown. Some inorganic solids dissociate - or crack - into molecular species heating or upon dissolving, e.g. Aluminium chloride. In such cases it is helpful to depict both the molecular and the nonmolecular forms.
In crystallography, a Strukturbericht designation or Strukturbericht type is a system of detailed crystal structure classification by analogy to another known structure. The designations were intended to be comprehensive but are mainly used as supplement to space group crystal structures designations, especially historically.
The structure of the pyridine complex has been determined crystallographically. [2] Adducts with other N-heterocycles have also been characterized similarly. [3] Aqueous chromium(VI) oxide peroxide decomposes in a few seconds, turning green as chromium(III) compounds are formed. [4] 2 CrO(O 2) 2 + 7 H 2 O 2 + 6 H + → 2 Cr 3+ + 10 H 2 O + 7 O 2
Structure of an octahedral metal aquo complex. Chromium(II) ion in aqueous solution. Most aquo complexes are mono-nuclear, with the general formula [M(H 2 O) 6] n+, with n = 2 or 3; they have an octahedral structure. The water molecules function as Lewis bases, donating a pair of electrons to the metal ion and forming a dative covalent bond ...