Ium

ium is a suffix widely used in the names of chemical elements. In English and many other languages, many element names end with -ium, reflecting a long-standing convention in chemical nomenclature. The suffix comes from Latin -ium, a neuter noun ending, and was adopted into modern element naming during the 18th and 19th centuries. Names ending in -ium are especially common among metals and metalloids and among many heavier or synthetic elements.

Examples include helium, lithium, beryllium, magnesium, calcium, titanium, chromium, zirconium, uranium, neptunium, plutonium, americium, curium, berkelium, californium, einsteinium, fermium, mendelevium, nobelium, lawrencium and roentgenium. By contrast, several familiar elements do not end with -ium, such as carbon, nitrogen, oxygen, fluorine, neon, argon, krypton, xenon, radon and hydrogen. The -ium suffix has no chemical meaning by itself; it is a historical naming convention that helps identify many metallic and post-transition elements, and it remains in use in the official nomenclature for newly discovered elements under the IUPAC system.