Carbon monoxide, CO, is an important ligand in coordination chemistry. When CO is reacted with nickel metal, the product is \(\left[\mathrm{Ni}(\mathrm{CO})_{4}\right],\) which is a toxic, pale yellow liquid. (a) What is the oxidation number for nickel in this compound? (b) Given that \(\left[\mathrm{Ni}(\mathrm{CO})_{4}\right]\) is a diamagnetic molecule with a tetrahedral geometry, what is the electron configuration of nickel in this compound? (c) Write the name for \(\left[\mathrm{Ni}(\mathrm{CO})_{4}\right]\) using the nomenclature rules for coordination compounds.

To determine the oxidation number of nickel in the molecule, we need to consider the charge of its ligands, CO. In this case, CO is a neutral ligand, as it doesn't have any charge. Since the molecule itself is neutral (not charged), the oxidation number of nickel is 0, as it is surrounded by neutral ligands.

Nickel is a transition metal with an atomic number of 28. The electron configuration for neutral nickel is \([\mathrm{Ar}]\,3d^8\,4s^2\). To explain the diamagnetic property of \(\left[\mathrm{Ni}(\mathrm{CO})_{4}\right]\), we need to analyze the d-orbitals. Since the molecule is diamagnetic, all the d-orbitals must be paired to ensure no unpaired electrons are present. The ligands occupy four orbitals in \((sp^3)-d\) hybridization. The neutral nickel has two electrons in the 4s orbital and eight electrons in the 3d orbital. The four CO ligands donate four electrons to the nickel atom, filling the 3d orbital and leaving the 4s orbital empty. The electron configuration of nickel in this compound is thus \([\mathrm{Ar}]\,3d^{10}\).

According to the nomenclature rules for coordination compounds, we name the ligands first, followed by the metal name. When naming ligands, neutral ligands are named as they are, while anionic ligands use the suffix "-o." In this case, the ligand is CO, which is neutral, so its name remains unchanged. The metal is nickel, and since the oxidation number is 0, we don't need to add a Roman numeral after the metal name, as we normally would if it had a nonzero oxidation number. Thus, the name for \(\left[\mathrm{Ni}(\mathrm{CO})_{4}\right]\) is tetracarbonylnickel.