What determines the size of an ion in an octahedral complex?

[lord12]

An an octahedral complex with all strong field ligands, which ion has the larger radius, Fe2+ or Co2+? What are the rules for known the size of the ion with respect if its a weak or strong field ligand?

 

[Gokul43201]

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[Blueshift5]

The ion with the larger radius in this case would be Fe2+. The size of an ion is determined by the strength of its ligands, with stronger ligands resulting in a smaller ion and weaker ligands resulting in a larger ion. In this case, all strong field ligands in an octahedral complex would result in a smaller ion, so Fe2+ would have a larger radius compared to Co2+ with the same ligands. This is because strong field ligands cause a greater splitting of the d orbitals, resulting in a higher energy and a more compact ion. In contrast, weak field ligands do not cause as much splitting and therefore result in a larger ion.