The coordination sphere is [Fe(CN)₆]⁴⁻, and the counter ion is K⁺ in the complex K₄[Fe(CN)₆]. The entire coordination compound is enclosed in square brackets.

The oxidation number of the central atom in a complex is defined by considering the charge it would have if all ligands and shared electron pairs are removed. It is represented by a Roman numeral in parenthesis following the coordination ...

Homoleptic complexes, like [Co(NH₃)₆]³⁺, involve a metal bound to only one kind of donor group. Heteroleptic complexes, such as [Co(NH₃)₄Cl₂]⁺, feature a metal bound to more than one kind of donor group.

The lanthanoid contraction causes the radii of the third transition series elements to be very similar to those of the corresponding second series elements. The nearly identical radii of Zr (160 pm) and Hf (159 pm), resulting from the lanthanoid ...

The lanthanoid contraction is caused by imperfect shielding of one electron by another in the same sub-shell. While the decrease in atomic radii is not quite regular, M³⁺ ions exhibit a more regular contraction. This is attributed to the imperfect ...