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
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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
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McMurry 8th EditionCh.21 - Transition Elements and Coordination ChemistryProblem 21.113
McMurry 8th EditionCh.21 - Transition Elements and Coordination ChemistryProblem 21.113Chapter 21, Problem 21.113
For each of the following complexes, draw a crystal field energy-level diagram, assign the electrons to orbitals, and predict the number of unpaired electrons.
(d) [Cu(en)2]2+ (square planar)
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Identify the metal ion and its oxidation state. Copper in [Cu(en)_2]^{2+} is in the +2 oxidation state, so it is Cu^{2+}.
Determine the electron configuration of the Cu^{2+} ion. Copper has an atomic number of 29, so its electron configuration is [Ar] 3d^{10} 4s^1. For Cu^{2+}, remove two electrons, resulting in [Ar] 3d^9.
Recognize that the complex is square planar, which typically involves dsp^2 hybridization. In square planar complexes, the d_{x^2-y^2} orbital is the highest in energy.
Draw the crystal field splitting diagram for a square planar complex. The order of energy levels from highest to lowest is: d_{x^2-y^2}, d_{xy}, d_{z^2}, d_{xz}, d_{yz}.
Assign the 9 d-electrons of Cu^{2+} to the orbitals in the crystal field diagram, starting from the lowest energy level. Predict the number of unpaired electrons based on the electron configuration.
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Key Concepts
Here are the essential concepts you must grasp in order to answer the question correctly.
Crystal Field Theory
Crystal Field Theory (CFT) explains how the arrangement of ligands around a central metal ion affects the energy levels of its d-orbitals. In octahedral or square planar complexes, the d-orbitals split into different energy levels due to the electrostatic interactions between the ligands and the d-electrons. Understanding this splitting is crucial for predicting the electronic configuration and magnetic properties of the complex.
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The study of ligand-metal interactions helped to form Ligand Field Theory which combines CFT with MO Theory.
Electron Configuration
Electron configuration refers to the distribution of electrons in an atom's orbitals. For transition metals, this involves filling the d-orbitals according to the Aufbau principle, Hund's rule, and the Pauli exclusion principle. In the case of [Cu(en)2]2+, knowing the electron configuration of copper and how it changes upon complex formation is essential for determining the number of unpaired electrons.
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Unpaired Electrons and Magnetism
Unpaired electrons are electrons that occupy an orbital alone rather than in pairs. The presence of unpaired electrons in a complex contributes to its magnetic properties; complexes with unpaired electrons are paramagnetic, while those with all paired electrons are diamagnetic. Identifying the number of unpaired electrons in [Cu(en)2]2+ helps predict its magnetic behavior and is a key aspect of understanding its chemical properties.
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Related Practice
Textbook Question
What is the electron configuration of Co2+ and how many unpaired electrons are in the free transition metal ion?
(a) [Ar]3d54s2; 5 unpaired electrons
(b) [Ar]3d54s2; 1 unpaired electron
(c) [Ar]3d7; 3 unpaired electrons
(d) [Ar]3d7; 1 unpaired electron
Textbook Question
What role does EDTA4- play as a trace additive to mayonnaise? Would the glycinate ion (H2NCH2CH2NH2) be an effective substitute for EDTA4-?
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
Which of the following complexes are diamagnetic?
(a) [Ni(H2O)6]2+
(b) [Co(CN)6]3-
(c) [HgI4]2- (tetrahedral)
(d) [Cu(NH3)4]2+ (square planar)
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.