Lanthanon is a term that refers to a group of metallic chemical elements in the periodic table. There are several synonyms for this term, including the rare-earth metals, rare-earth elements, and rare-earth minerals. The lanthanon series consists of 15 chemical elements, including cerium, praseodymium, neodymium, promethium, europium, gadolinium, terbium, dysprosium, holmium, erbium, thulium, ytterbium, lutetium, scandium, and yttrium. These elements all have similar chemical properties and are often found together in rare-earth minerals, which are used in various industries such as electronics, ceramics, and magnets. Understanding the terminology associated with these elements is essential for anyone working in these fields.