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23 Transition Metals and Solutions to Exercises Coordination Chemistry (c) A visible absorption spectrum shows the amount of light absorbed at a given wavelength. It is a plot of absorbance (dependent variable, y-axis) wavelength (independent variable, x-axis). (d) E(J/photon) = hv = Change J/photon to kJ/mol. E = 440 nm 3.00 m = = J/photon 4.5177 photon 6.022 mol = kJ/mol 23.47 No. The ion has 6 d-electrons. In an octahedral crystal field, the energies of the d orbitals are split three and two. That is, the dxy, and dyz orbitals are lower in energy than the free ion, and the and orbitals are higher in energy. In a low- spin complex, the d-electrons are paired to the maximum possible extent. All 6 d- electrons in a low-spin octahedral complex will pair and occupy the low energy dxy, and dyz orbitals. With no unpaired electrons, the complex cannot be paramagnetic. 23.48 No. The d-electrons of a transition metal complex will occupy orbitals with equal energy singly before they pair in any single orbital. The possibilities for unpaired electrons depends on the geometry of the complex and the nature (high- or low-spin) of the ligands. 23.49 Most of the electrostatic interaction between a metal ion and a ligand is the attractive interaction between a positively charged metal cation and the full negative charge of an anionic ligand or the partial negative charge of a polar covalent ligand. Whether the interaction is ion-ion or ion-dipole, the ligand is strongly attracted to the metal center and can be modeled as a point negative charge. 23.50 Six ligands in an octahedral arrangement are oriented along the y, and Z axes of the metal. These negatively charged ligands (or the negative end of ligand dipoles) have greater electrostatic repulsion with valence electrons in metal orbitals that also lie along these axes, the and d The and metal orbitals point between the x, y, and axes, and electrons in these orbitals experience less repulsion with ligand electrons. Thus, in the presence of an octahedral ligand field, the dxy, and dxy metal orbitals are lower in energy than the and 23.51 (a) dxy, (b) The magnitude of and the energy of the d-d transition for a d¹ complex are equal. (c) 6.626 10⁻³⁴ 3.00 S m 1x 1nm 10⁻⁹ m 6.022 mol photons = 704