All practice pages/Interatomic theory/Elements
Element 58, a lanthanide
The most abundant rare earth, the spark in a lighter flint, and the powder that polishes glass.
Period 6, in the lanthanide row set below the main table. The other lanthanides are tinted, and every cell opens its own article.
Cerium has 58 electrons, one for every proton, so the atom carries no charge. Below are the same 58 electrons written two ways.
1s² 2s² 2p⁶ 3s² 3p⁶ 3d¹⁰ 4s² 4p⁶ 4d¹⁰ 4f¹ 5s² 5p⁶ 5d¹ 6s²
Short form: [Xe] 4f¹ 5d¹ 6s², where [Xe] stands for the 54 electrons xenon already has.
That list runs by shell. In the order the subshells fill it reads [Xe] 6s² 4f¹ 5d¹, because a subshell fills by its energy, not by its shell number.
The simple form counts electrons shell by shell. The orbital form says which subshell each one sits in: s holds 2, p holds 6, d holds 10 and f holds 14. Shell 4 here is 4s² 4p⁶ 4d¹⁰ 4f¹, and 2 + 6 + 10 + 1 is 19.
Cerium sits in period 6 and has 6 shells. The period number counts the shells.
The outer shell holds 2 electrons. Those are the ones cerium can lose, gain or share, so they are the ones that decide what it bonds with.
Unusually for a lanthanide, cerium readily forms Ce⁴⁺ as well as Ce³⁺, because losing a fourth electron leaves it with the same stable electron arrangement as xenon.
More abundant in the crust than copper. It is the main rare earth in bastnäsite and monazite, mined mostly in China and at Mountain Pass, California.
Jöns Jacob Berzelius and Wilhelm Hisinger in Sweden, and independently Martin Heinrich Klaproth in Germany, found it in 1803. It was named after the asteroid Ceres, discovered two years earlier.
Cerium oxide is the standard powder for polishing glass, from lenses to phone screens. Cerium also goes into catalytic converters and self-cleaning oven walls, and ferrocerium, an alloy that throws hot sparks when scratched, makes lighter flints and fire starters.