The coordination complex [Cr(CO)₆] forms colorless, diamagnetic crystals that melt at 90 °C
a. What is the oxidation number of chromium in this compound?
d. Write the name for [Cr(CO)₆] using the nomenclature rules for coordination compounds.

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Identify the ligands in the coordination complex. In [Cr(CO)6], the ligand is carbon monoxide (CO), which is a neutral ligand.

Determine the charge of the ligands. Since CO is a neutral ligand, it contributes a charge of 0 to the complex.

Calculate the overall charge of the complex. [Cr(CO)6] is a neutral complex, meaning the sum of the oxidation state of chromium and the charges of the ligands is zero.

Set up the equation for the oxidation state of chromium. Let x be the oxidation state of chromium. Since the complex is neutral and CO is neutral, the equation is x + 6(0) = 0.

Solve for x to find the oxidation state of chromium. Since the equation simplifies to x = 0, the oxidation state of chromium in [Cr(CO)6] is 0. The name of the compound is hexacarbonylchromium(0).

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Key Concepts

Here are the essential concepts you must grasp in order to answer the question correctly.

Oxidation Number

The oxidation number is a measure of the degree of oxidation of an atom in a compound. It indicates the number of electrons that an atom can gain, lose, or share when forming chemical bonds. In coordination complexes, the oxidation state of the central metal ion can be determined by considering the charges of the ligands and the overall charge of the complex.

Coordination Complex

A coordination complex consists of a central metal atom or ion bonded to surrounding molecules or ions known as ligands. The ligands can be neutral or charged and donate electron pairs to the metal, forming coordinate covalent bonds. The geometry and properties of the complex depend on the metal's oxidation state and the nature of the ligands.

Nomenclature of Coordination Compounds

The nomenclature of coordination compounds follows specific rules established by the International Union of Pure and Applied Chemistry (IUPAC). The name typically starts with the ligands listed in alphabetical order, followed by the name of the metal with its oxidation state indicated in Roman numerals. For example, in [Cr(CO)6], 'carbonyl' is the ligand, and the name would be 'hexacarbonylchromium(0)' indicating the oxidation state of chromium.

The coordination complex [Cr(CO)6] forms colorless, diamagnetic crystals that melt at 90 °Ca. What is the oxidation number of chromium in this compound?d. Write the name for [Cr(CO)6] using the nomenclature rules for coordination compounds.