Textbook Question
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.
Ch.21 - Transition Elements and Coordination Chemistry
McMurry8th EditionChemistryISBN: 9781292336145
Not the one you use?Change textbookSelect a different textbook
Table of contents
- Ch.1 - Chemical Tools: Experimentation & Measurement170
- Ch.2 - Atoms, Molecules & Ions160
- Ch.3 - Mass Relationships in Chemical Reactions169
- Ch.4 - Reactions in Aqueous Solution199
- Ch.5 - Periodicity & Electronic Structure of Atoms102
- Ch.6 - Ionic Compounds: Periodic Trends and Bonding Theory92
- Ch.7 - Covalent Bonding and Electron-Dot Structures61
- Ch.8 - Covalent Compounds: Bonding Theories and Molecular Structure59
- Ch.9 - Thermochemistry: Chemical Energy122
- Ch.10 - Gases: Their Properties & Behavior155
- Ch.11 - Liquids & Phase Changes54
- Ch.12 - Solids and Solid-State Materials73
- Ch.13 - Solutions & Their Properties120
- Ch.14 - Chemical Kinetics98
- Ch.15 - Chemical Equilibrium125
- Ch.16 - Aqueous Equilibria: Acids & Bases110
- Ch.17 - Applications of Aqueous Equilibria147
- Ch.18 - Thermodynamics: Entropy, Free Energy & Equilibrium86
- Ch.19 - Electrochemistry154
- Ch.20 - Nuclear Chemistry96
- Ch.21 - Transition Elements and Coordination Chemistry156
- Ch.22 - The Main Group Elements187
- Ch.23 - Organic and Biological Chemistry51
All textbooks
McMurry 8th EditionCh.21 - Transition Elements and Coordination ChemistryProblem 21.116
McMurry 8th EditionCh.21 - Transition Elements and Coordination ChemistryProblem 21.116Chapter 21, Problem 21.116
Although Cl- is a weak-field ligand and CN- is a strong field ligand, [CrCl6]3- and [Cr(CN)6]3- exhibit approximately the same amount of paramagnetism. Explain.
Verified step by step guidance1
Identify the oxidation state of chromium in both complexes. Chromium is in the +3 oxidation state in both [CrCl_6]^{3-} and [Cr(CN)_6]^{3-}.
Determine the electron configuration of the Cr^{3+} ion. Chromium has an atomic number of 24, so its electron configuration is [Ar] 3d^5 4s^1. For Cr^{3+}, remove three electrons, resulting in [Ar] 3d^3.
Consider the effect of ligand field strength on the d-orbitals. Cl^- is a weak-field ligand, leading to a high-spin complex, while CN^- is a strong-field ligand, typically leading to a low-spin complex.
Analyze the number of unpaired electrons. In both complexes, the Cr^{3+} ion has three unpaired electrons in the 3d orbitals, resulting in similar paramagnetic properties.
Conclude that despite the difference in ligand field strength, the number of unpaired electrons remains the same in both complexes, explaining the similar paramagnetism.
Verified video answer for a similar problem:
This video solution was recommended by our tutors as helpful for the problem above.
Was this helpful?
Key Concepts
Here are the essential concepts you must grasp in order to answer the question correctly.
Ligand Field Theory
Ligand Field Theory explains how the presence of ligands around a central metal ion affects its electronic structure and the energy levels of its d-orbitals. Strong-field ligands, like CN<sup>-</sup>, cause a larger splitting of d-orbitals compared to weak-field ligands, like Cl<sup>-</sup>. This theory helps in understanding the magnetic properties of coordination complexes based on the arrangement and strength of the ligands.
Recommended video:
Guided course
02:40
Strong-Field Ligands result in a large Δ and Weak-Field Ligands result in a small Δ.
Paramagnetism
Paramagnetism is a form of magnetism that occurs in materials with unpaired electrons. In coordination complexes, the number of unpaired electrons determines the degree of paramagnetism. Both [CrCl<sub>6</sub>]<sup>3-</sup> and [Cr(CN)<sub>6</sub>]<sup>3-</sup> can exhibit similar levels of paramagnetism if they have the same number of unpaired electrons, despite the differences in ligand strength.
Recommended video:
Guided course
01:33Paramagnetism and Diamagnetism
Crystal Field Splitting
Crystal Field Splitting refers to the energy difference between the split d-orbitals in a transition metal complex due to the presence of ligands. In octahedral complexes, the d-orbitals split into two sets: t<sub>2g</sub> and e<sub>g</sub>. The extent of this splitting influences the electron configuration and, consequently, the magnetic properties of the complex, which can lead to similar paramagnetic behavior in complexes with different ligands.
Recommended video:
Guided course
03:04The crystal field splitting pattern for octahedral complexes has the d orbitals on or along the axes as having the higher energy.
Related Practice
Textbook Question
The glycinate anion, gly-= NH2CH2CO2 -, bonds to metal ions through the N atom and one of the O atoms. Using to represent gly-, sketch the structures of the four stereoisomers of Co(gly)3.
Textbook Question
What is the oxidation state of the metal in each of the complexes?
a. [Ni(CN)5]3–
b. Ni(CO)4
c. [Co(en)2(H2O)Br]2+
d. [Cu(H2O)2(C2O4)2]2–
e. Co(NH3)3(NO2)3
Textbook Question
Draw the structures of all possible diastereoisomers of an octahedral complex with the formula MA2B2C2. Which of the diastereoisomers, if any, can exist as enantiomers?
Textbook Question
The Ni2+(aq) cation is green, but Zn2+(aq) is colorless. Explain.
Textbook Question
Predict the crystal field energy-level diagram for a square pyramidal ML5 complex that has two ligands along the axes but only one ligand along the z axis. Your diagram should be intermediate between those for an octahedral ML6 complex and a square planar ML4 complex.