The [Cr(H₂O)₆]³⁺ ion is violet, and [Cr(CN)₆]^3- is yellow. Explain this difference using crystal field theory. Use the colors to order H₂O and CN^- in the spectrochemical series.

검증된 단계별 안내

Step 1: Understand that the color of a complex ion is due to the absorption of light which promotes an electron from a lower energy d-orbital to a higher energy d-orbital. The color we see is the complementary color of the light absorbed.

Step 2: Recognize that the crystal field theory explains the color of transition metal complexes in terms of the splitting of their d-orbitals into two sets of different energies when ligands approach the metal ion. The difference in energy between these two sets of d-orbitals corresponds to the energy of light absorbed.

Step 3: Realize that the extent of splitting of the d-orbitals, and hence the color of the complex, depends on the nature of the ligands. Ligands that cause a large splitting of the d-orbitals are known as strong-field ligands, while those that cause a small splitting are known as weak-field ligands.

Step 4: Infer from the given colors that [Cr(H₂O)₆]³⁺ absorbs light of higher energy (shorter wavelength) than [Cr(CN)₆]^3-. This is because violet light is the complementary color of yellow light, which is of lower energy (longer wavelength). Therefore, H₂O is a weaker field ligand than CN^-.

Step 5: Conclude that in the spectrochemical series, which orders ligands according to their ability to split the d-orbitals, H₂O comes before CN^-.

비슷한 문제에 대한 검증된 영상 답변:

이 영상 해법은 위 문제에 도움이 된다고 튜터들이 추천한 것입니다.

주요 개념

질문에 올바르게 답하기 위해 반드시 이해해야 하는 핵심 개념들은 다음과 같습니다.

Crystal Field Theory

Crystal Field Theory (CFT) explains the electronic structure of transition metal complexes by considering the effect of surrounding ligands on the d-orbitals of the metal ion. When ligands approach the metal ion, they create an electric field that splits the degenerate d-orbitals into different energy levels. The extent of this splitting depends on the nature of the ligands and their arrangement around the metal ion.

Spectrochemical Series

The spectrochemical series is a list that ranks ligands based on the strength of the field they produce when coordinating to a metal ion. Strong field ligands, like CN-, cause a larger splitting of the d-orbitals, leading to higher energy transitions and different colors. Conversely, weak field ligands, such as H2O, result in smaller splitting and lower energy transitions, which can be observed in the color of the complexes.

Color and d-Orbital Splitting

The color observed in transition metal complexes is a result of the specific wavelengths of light absorbed during electronic transitions between split d-orbitals. The energy difference between these orbitals corresponds to specific colors in the visible spectrum. For example, the violet color of [Cr(H2O)6]3+ indicates that it absorbs light in the yellow-green region, while the yellow color of [Cr(CN)6]3- suggests it absorbs light in the violet region, reflecting the differences in ligand field strength.

The [Cr(H2O)6]3+ ion is violet, and [Cr(CN)6]3- is yellow. Explain this difference using crystal field theory. Use the colors to order H2O and CN- in the spectrochemical series.