What metal is known to form primarily colorless compounds?

Scandium is known to primarily form colorless compounds due to its electronic configuration and the characteristics of its cations. Scandium typically exists in the +3 oxidation state, where it has an electron configuration of [Ar]3d^1. This configuration leads to weak interactions and minimal ligand field splitting, which results in the absence of strong color-producing d-d transitions. Consequently, compounds of scandium, such as scandium(III) chloride or scandium(III) oxide, tend to be colorless in solution and as solids.

In contrast, the other metals listed often form colored compounds. For example, copper compounds frequently display vibrant colors due to the presence of partially filled d-orbitals, allowing for d-d transitions. Similarly, iron can exist in several oxidation states, including +2 and +3, and its compounds can appear in various colors based on the environment of the metal ions. Zinc forms some colored compounds as well, especially when interacted with other ligands, but its primary compounds, such as zinc oxide, are often colorless. However, these characteristics do not match the defining trait of scandium's compound formation, which is predominantly colorless.