How does the size of the ions relate to bond distance in high oxidation states?

The relationship between ion size and bond distance, particularly in high oxidation states, is well-understood through the concept of effective nuclear charge and ionic radii. In high oxidation states, cations typically have lost a significant number of electrons, resulting in a reduced electron-electron repulsion and an increased effective nuclear charge acting on the remaining electrons. This effect often leads to a contraction of the ionic radius.

Smaller ions, resulting from higher oxidation states, possess a stronger attraction to neighboring anions due to their increased charge density. This stronger electrostatic attraction pulls the ions closer together, which consequently reduces the bond distance between them. The decrease in size allows for a more compact arrangement in the crystal lattice, thus creating shorter bond distances.

In contrast, larger ions are less able to approach their counterparts closely due to increased electron-electron repulsion and a smaller effective nuclear charge per electron. Therefore, their interactions lead to larger bond distances.

This understanding aligns with the principle that smaller ions result in stronger and shorter bonding interactions, particularly evident in compounds formed by transition metals or lanthanides in high oxidation states, where ionic sizes can considerably differ based on their charge states.