Chapter 20: Problem 151
In the coordination compound \(\mathrm{K}_{4}\left[\mathrm{Ni}(\mathrm{CN})_{4}\right]\), the oxidation state of nickel is (a) \(-1\) (b) 0 (c) \(+1\) (d) \(+2\)
Short Answer
Expert verified
The oxidation state of nickel is 0.
Step by step solution
01
Identify components of the complex
The coordination compound is \( \mathrm{K}_{4}\left[\mathrm{Ni}(\mathrm{CN})_{4}\right] \). It contains potassium (K), nickel (\(Ni\)), and the cyanide ligand (\(\mathrm{CN}^{-}\)).
02
Determine potassium's contribution
Potassium (\(\mathrm{K}\)) is a metal that commonly forms a \(+1\) charge. Since there are 4 potassium ions, the total charge contribution from potassium is \(+4\).
03
Define the known charge of cyanide
The cyanide ion (\(\mathrm{CN}^{-}\)) has a charge of \(-1\). Since there are four cyanide ions in the complex \(\left(\mathrm{Ni}(\mathrm{CN})_{4}\right)\), their total charge is \(-4\).
04
Calculate the charge balance
The overall compound is neutral, so the sum of the charges from the ions must equal zero: \[ x + 4(+1) + 4(-1) = 0 \] where \(x\) is the oxidation state of nickel. Simplifying, we have \[ x + 4 - 4 = 0 \] which reduces to \(x = 0\).
05
Conclude with nickel's oxidation state
The oxidation state of nickel (\(Ni\)) in the compound is 0, following the calculation from charge balances in the complex.
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Key Concepts
These are the key concepts you need to understand to accurately answer the question.
Oxidation State
The oxidation state of an element in a compound indicates the hypothetical charge that an atom would have if all bonds to atoms of different elements were fully ionic. For the compound \( \mathrm{K}_{4}\left[\mathrm{Ni}(\mathrm{CN})_{4}\right] \), the oxidation state of nickel (\(Ni\)) is - our primary focus.
When we look at the potassium part, it has an oxidation state of "+1" which is standard in its compounds. Since there are four potassium ions, the total contribution is "+4". The cyanide ion (\(\mathrm{CN}^{-}\)) contributes a "-1" charge. With four cyanide ions, their total contribution is "-4". To figure out the oxidation state of nickel, the compound is known to be neutral overall (\(0\)) so: \[ x + 4 - 4 = 0 \] where \(x\) is the oxidation state of nickel. Solving this gives \(x = 0\). Thus, we determine the oxidation state of nickel is zero.
Charge Balance
Charge balance in coordination compounds is crucial for their stability and neutrality. In the case of \( \mathrm{K}_{4}\left[\mathrm{Ni}(\mathrm{CN})_{4}\right] \), the overall charge must be zero to maintain neutrality.
- Cations such as potassium (\( \mathrm{K}^{+} \)) have positive charges, here it contributes a "+4" total charge from four potassium ions.
- An ions like cyanide (\(\mathrm{CN}^{-}\)) contribute negative charges; four of these contribute a "-4" total.
Ligands
Ligands play a fundamental role in coordination compounds. They are ions or molecules that can donate a pair of electrons to the central metal atom, forming a coordination bond. In the compound \( \mathrm{K}_{4}\left[\mathrm{Ni}(\mathrm{CN})_{4}\right] \), the ligand involved is cyanide (\(\mathrm{CN}^{-}\)).
- Cyanide is known as a strong field ligand, meaning it exerts a significant crystal field splitting, affecting the electronic properties of the central metal, nickel in this case.
- Cyanide donates an electron pair, forming a coordination bond with nickel, thereby helping to determine the geometry and properties of the complex.
Transition Metals
Transition metals, such as nickel in \( \mathrm{K}_{4}\left[\mathrm{Ni}(\mathrm{CN})_{4}\right] \), are characterized by their ability to form various oxidation states and complex ions. They lie in the d-block of the periodic table and have partially filled d orbitals.
- The rich chemistry of transition metals allows them to form stable coordination compounds with different ligands due to their flexible oxidation states.
- These metals also participate in numerous physical and chemical processes due to their unique ability to engage in electron sharing through d orbitals.