Smoky quartz has distinctive lavender and purple colors due...

Smoky quartz has distinctive lavender and purple colors due to the presence of manganese impuritics in crystals of silicon dioxide. Which of the orbital diagrams in Figure $\mathrm{P} 22.4$ best describes the $\mathrm{Mn}^{2+}$ ion in a tetrahedral field?

Key Concepts

Crystal Field Theory

Crystal Field Theory explains how the degenerate d orbitals of a transition metal ion split into groups of different energy levels when surrounded by a set of ligands. This energy splitting depends on the geometry of the coordination complex and underlies much of the complex's optical, magnetic, and chemical properties.

Tetrahedral Coordination Geometry

In a tetrahedral coordination geometry, the arrangement of ligands around the metal leads to a specific splitting of the d orbitals into two sets: the lower-energy e set and the higher-energy t2 set. The overall splitting energy (?t) in tetrahedral fields is smaller than that in octahedral fields, which often results in high-spin configurations.

High-Spin d5 Configuration

A high-spin d5 configuration, as found in Mn2+ ions, involves five electrons occupying all five separate d orbitals unpaired in a tetrahedral field. Due to the relatively small crystal field splitting, electrons prefer to remain unpaired rather than pair up, which affects the magnetic behavior of the ion.

Manganese(II) Ion Electron Configuration

The Mn2+ ion has five d electrons (d5 configuration) that, when placed in the tetrahedral field, distribute into the split d orbitals. This leads to a high-spin state with all electrons unpaired, playing a key role in determining the ion’s magnetic and spectroscopic characteristics.

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