Cerium, represented by the symbol Ce and with an atomic number of 58, is a member of the lanthanide series in Group 3 of the periodic table. It has an atomic mass of 140.12 g/mol and is classified in the f-block, with the electron configuration of [Xe] 6s² 4f¹. Cerium was discovered in 1803 by chemists Jöns Jacob Berzelius and Wilhelm Hisinger. The element's name is derived from the asteroid Ceres, which was identified shortly before the element's discovery.
Cerium is an inner transition metal in the lanthanide series, characterised by its silvery-white appearance. Although cerium is a soft, malleable, and ductile metal, it is relatively harder than lead.
As a rare earth metal, cerium ranks 25th in abundance, with an average distribution of 20-60 parts per million (ppm), making it the most abundant among the lanthanides. Cerium has anti-inflammatory, anti-angiogenic, and antioxidant qualities that aid in lowering oxidative stress, which is connected to several illnesses. Foods including orange bell peppers, cucumbers, spinach, and black-eyed peas contain it.
Cerium has a short half-life of 1.02 seconds for certain radioactive isotopes.
Cerium can form a variety of compounds, including cerium(III) oxide (Ce₂O₃), cerium(IV) oxide (CeO₂), and cerium chloride (CeCl₃).
At room temperature, it readily oxidises to form cerium(IV) oxide:
Ce+O2→CeO2
When cerium reacts with hydrofluoric acid (HF), it forms a protective layer of cerium fluoride:
2Ce + 6HF → 2CeF3 + 3H2↑
(Session 2025 - 26)