Which lanthanide has atomic number 58?

Which lanthanide has atomic number 58? Cerium does. Its chemical symbol is Ce, and it occupies the second position in the commonly listed lanthanide series, after lanthanum and before praseodymium.

Cerium is a soft, silvery-white rare-earth metal. It was discovered in 1803 by Jöns Jakob Berzelius and Wilhelm Hisinger in Sweden, independently of Martin Heinrich Klaproth in Germany. The element was named after Ceres, an asteroid discovered two years earlier and then regarded as a planet.

Cerium is especially notable among the lanthanides because it commonly forms both +3 and +4 oxidation states. That chemistry helps separate it from other rare-earth elements and supports uses such as glass polishing and catalytic converters. Cerium oxide is also used in polishing powders, while cerium-containing alloys produce the sparks in ferrocerium lighter flints.

A common mix-up is confusing cerium with lanthanum, atomic number 57, or praseodymium, atomic number 59. The number 58 uniquely identifies cerium: it represents the 58 protons in every cerium atom.