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Chromium compounds are compounds containing the element chromium (Cr). Chromium is a member of group 6 of the transition metals . The +3 and +6 states occur most commonly within chromium compounds, followed by +2; charges of +1, +4 and +5 for chromium are rare, but do nevertheless occasionally exist.
When a salt of a metal ion, with the generic formula MX n, is dissolved in water, it will dissociate into a cation and anions. [citation needed]+ + (aq) signifies that the ion is aquated, with cations having a chemical formula [M(H 2 O) p] q+ and anions whose state of aquation is generally unknown.
Chromium(III) hydroxide is a gelatinous green inorganic compound with the chemical formula Cr(OH) 3. It is a polymer with an undefined structure and low solubility. It is amphoteric, dissolving in both strong alkalis and strong acids. [2] In alkali: Cr(OH) 3 + OH − → CrO − 2 + 2 H 2 O In acid: Cr(OH) 3 (OH 2) 3 + 3 H + → Cr(OH 2) 6 3+
Several of the CPK colors refer mnemonically to colors of the pure elements or notable compound. For example, hydrogen is a colorless gas, carbon as charcoal, graphite or coke is black, sulfur powder is yellow, chlorine is a greenish gas, bromine is a dark red liquid, iodine in ether is violet, amorphous phosphorus is red, rust is dark orange-red, etc.
Naturally occurring chromium is composed of four stable isotopes; 50 Cr, 52 Cr, 53 Cr and 54 Cr, with 52 Cr being the most abundant (83.789% natural abundance). 50 Cr is observationally stable , as it is theoretically capable of decaying to 50 Ti via double electron capture with a half-life of no less than 1.3 × 10 18 years.
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.
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The formula, Cu 2 CO 3 (OH) 2 shows that it is halfway between copper carbonate and copper hydroxide. Indeed, in the past the formula was written as CuCO 3 ·Cu(OH) 2. The crystal structure is made up of copper, carbonate and hydroxide ions. [37] The mineral atacamite is an example of a basic chloride. It has the formula, Cu 2 Cl(OH) 3.