All practice pages/Interatomic theory/Elements
Element 57, a lanthanide
The first of the lanthanides, the row of look-alike metals that takes its name, and a working part of many hybrid car batteries.
Period 6, in the lanthanide row set below the main table. The other lanthanides are tinted, and every cell opens its own article.
Lanthanum has 57 electrons, one for every proton, so the atom carries no charge. Below are the same 57 electrons written two ways.
1s² 2s² 2p⁶ 3s² 3p⁶ 3d¹⁰ 4s² 4p⁶ 4d¹⁰ 5s² 5p⁶ 5d¹ 6s²
Short form: [Xe] 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 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 3 here is 3s² 3p⁶ 3d¹⁰, and 2 + 6 + 10 is 18.
Lanthanum sits in period 6 and has 6 shells. The period number counts the shells.
The outer shell holds 2 electrons. Those are the ones lanthanum can lose, gain or share, so they are the ones that decide what it bonds with.
Like the other lanthanides, it gives up three electrons to form the La³⁺ ion in most of its compounds.
Found with the other rare earths in monazite and bastnäsite, mined mostly in China, the United States, Australia and Myanmar.
Carl Gustaf Mosander found it in 1839 hidden in cerium nitrate, which he had thought was pure. He named it from the Greek lanthanein, to lie hidden.
Nickel-metal hydride batteries in hybrid cars contain kilograms of a lanthanum-rich alloy. Lanthanum oxide makes high-quality camera and telescope lenses, lanthanum catalysts crack crude oil into gasoline, and lanthanum carbonate is a medicine that controls phosphate levels in kidney patients.