All practice pages/Interatomic theory/Elements
Element 32, a metalloid
The metalloid Mendeleev called eka-silicon, and the material of the very first transistor.
Period 4, group 14. The other metalloids are tinted, and every cell opens its own article.
Germanium has 32 electrons, one for every proton, so the atom carries no charge. Below are the same 32 electrons written two ways.
1s² 2s² 2p⁶ 3s² 3p⁶ 3d¹⁰ 4s² 4p²
Short form: [Ar] 3d¹⁰ 4s² 4p², where [Ar] stands for the 18 electrons argon already has.
That list runs by shell. In the order the subshells fill it reads [Ar] 4s² 3d¹⁰ 4p², 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.
Germanium sits in period 4 and has 4 shells. The period number counts the shells.
The outer shell holds 4 electrons. Those are the ones germanium can lose, gain or share, so they are the ones that decide what it bonds with. For a main-group element the group number gives that count: group 14 means 4.
Four valence electrons, like carbon and silicon. Germanium shares them in four covalent bonds, and in the pure crystal that arrangement makes it a semiconductor.
Rare and spread thin. It is recovered as a byproduct of zinc refining and from the ash of certain coals, mainly in China.
Clemens Winkler found it in 1886 in argyrodite, a silver mineral from Saxony, and named it after his homeland, Germany. Its atomic mass, density and oxide matched Mendeleev's 1871 predictions for eka-silicon almost exactly.
Fiber-optic cables, whose glass cores contain germanium dioxide; lenses and windows for infrared cameras and night vision; and high-efficiency solar cells for satellites. The first transistor, built at Bell Labs in 1947, was made of germanium.