What is a defining characteristic of transition metals in terms of their ions?

Transition metals are known for their ability to form colored ions in solution, which is a defining characteristic of these elements. The color observed in these ions arises from electronic transitions between d-orbitals. In transition metals, the d-orbitals can be split into different energy levels in the presence of ligands, leading to the absorption of specific wavelengths of light. The color of the solution is the result of the wavelengths that are not absorbed.

For example, when a transition metal ion interacts with water or other ligands, the electronic configuration can change, allowing electrons to transition between these split d-orbitals. This process results in the absorption of certain colors of light and the reflection of others, which is why transition metal solutions frequently display vivid colors, such as blue, green, or purple.

In contrast, the other statements do not accurately capture the properties of transition metals. Transition metals can exist in multiple oxidation states, leading to a variety of colored ions. They can also form both colored and colorless complexes, depending on the metal and its oxidation state. Additionally, transition metals are highly reactive and can form compounds with a broad range of elements. Thus, the characteristic ability to form colored ions in solution distinguishes transition metals from other groups in the periodic