Problem 77 - Chemistry The Central Science In Si Units

Question

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.

Step-by-Step Solution

Answer

Nickel's oxidation state is 0, its electron configuration is d^10, and the name is "tetracarbonyl nickel."

Step 1: Determine the Oxidation Number

In the coordination compound \([\mathrm{Ni}(obreak\mathrm{CO})_4]\), carbon monoxide (CO) is a neutral ligand. Therefore, it does not contribute any charge. Since the overall compound is neutral, the charge of nickel must also be neutral (0) to balance the whole compound. Thus, the oxidation number for nickel in this compound is 0.

Step 2: Analyze the Electron Configuration for Diamagnetism

Given that \([\mathrm{Ni}(obreak\mathrm{CO})_4]\) is a diamagnetic molecule, it must have all paired electrons. The atomic number of nickel is 28, with a ground state electron configuration of [Ar] 3d^8 4s^2. In the compound, with nickel having an oxidation state of 0, it retains this electron configuration. However, all electrons must be paired. Nickel in this compounds adopts an electron configuration which allows for paired electrons, leading to d^10 electron count (

Step 3: Apply Coordination Compound Naming Rules

When naming coordination compounds, the ligands are named first followed by the metal. "Carbonyl" is the name for the CO ligand in coordination chemistry, and since there are four carbonyl ligands, it is named as "tetracarbonyl." Nickel's oxidation state is 0, so no Roman numeral is needed for its charge. Thus, combining these descriptions, the name for \([\mathrm{Ni}(obreak\mathrm{CO})_4]\) is "tetracarbonyl nickel."

Key Concepts

Oxidation Number

The oxidation number is a concept used in chemistry to keep track of the electrons in a chemical compound. It indicates the charge of an atom if the compound were completely ionic. Oxidation numbers are essential for balancing chemical equations and understanding the changes during a chemical reaction.

In coordination chemistry, each ligand and the central metal atom have specific contributions to the overall charge of the compound. For \([xt[i}(\mathrm{CO})_4]\), carbon monoxide (CO) is known as a *neutral ligand*. Neutral ligands do not add any charge to the compound. Hence, the entire coordination compound remains neutral since CO as a ligand possesses no charge.

Therefore, if the compound itself has no overall charge, the oxidation state of nickel must also be zero, making it a neutral atom within the compound. This concept is vital in understanding how different parts of the compound balance each other to achieve stability.

Electron Configuration

Electron configuration describes how electrons are distributed in an atom's or compound's orbitals. Understanding electron configurations is crucial in chemistry as it provides insight into the chemical behavior of elements and compounds.

In the case of the coordination compound \([xt[i}(\mathrm{CO})_4]\), we know that the compound is *diamagnetic*. Diamagnetism is a form of magnetism where the substance does not retain any magnetic moment. For a compound to be diamagnetic, all electrons must be paired.

The atomic number of nickel is 28, and its ground state electron configuration is \[\text{[Ar]}\ 3d^8\ 4s^2\]. When nickel forms the \([xt[i}(\mathrm{CO})_4]\) compound, it retains its 0 oxidation state and adapts its electron configuration to ensure all electrons are paired, resulting in a \[3d^{10}\ 4s^0\text{ configuration}\], which is perfect for diamagnetism. This electron arrangement ensures maximum stability in the formed compound due to completed electron pairing.

Chemical Nomenclature

Chemical nomenclature is the system used for naming substances. In coordination compounds, nomenclature follows specific rules to make compound names systematic and universally understood.

For a compound like \([xt[i}(\mathrm{CO})_4]\), naming involves both the metal and the attached ligands. The naming convention states that the ligands are named before the metal. In this case, *carbonyl* is the term used for carbon monoxide when it is a ligand. Since there are four carbonyl ligands attached to nickel, we use the prefix "tetra-" to indicate this number, resulting in the term "tetracarbonyl."

The metal, nickel, in this compound has an oxidation state of 0, which means we do not include a Roman numeral in the name. As a result, the name of the compound is "tetracarbonyl nickel." Understanding chemical nomenclature is crucial as it allows chemists and scientists to communicate precise structural information solely through names.