cerous

Cerous refers to a chemical state where an element has a +3 oxidation state. This term is most commonly applied to the element cerium, which is a lanthanide. Cerium exhibits multiple oxidation states, but the +3 state, known as the cerous state, is its most stable and common form. In compounds where cerium is in the cerous state, it is often denoted by the symbol Ce(III). For example, cerous chloride has the chemical formula CeCl3. The cerous ion, Ce³⁺, has lost three electrons from its atomic structure. This oxidation state is characteristic of the lanthanide series, where the +3 oxidation state is generally the most prevalent due to the stability gained by achieving a filled or half-filled f-subshell in subsequent oxidation states. While cerium can also exist in a +4 oxidation state (ceric), the cerous state is the baseline and most frequently encountered. The properties of cerous compounds vary depending on the accompanying anion or ligand, but they generally share characteristics common to trivalent lanthanide ions.