Germanium is a Block P, Group 14, Period 4 element. The number of electrons in each of Germanium's shells is 2, 8, 18, 4 and its electronic configuration is [Ar] 3d¹⁰ 4s² 4p². In its elemental form germanium's CAS number is 7440-56-4. The germanium atom has a radius of 122.5.pm and it's Van der Waals radius is 200.pm. Germanium is not toxic. Germanium is a very important semiconductor. Zone-refining techniques have led to production of crystalline germanium for semiconductor use with extremely high purities. When germanium is doped with arsenic, gallium, or other elements, it is used as a transistor element in thousands of electronic applications. The most common use of germanium is as a semiconductor. Germanium is also finding many other applications including use as an alloying agent, as a phosphor in fluorescent lamps, and as a catalyst. Germanium and germanium oxide are transparent to the infrared and are used in infrared spectroscopes and other optical equipment, including extremely sensitive infrared detectors. The high refractive index and dispersion properties of its oxide's have made germanium useful as a component of wide-angle camera lenses and microscope objectives. The field of organo-germanium chemistry is becoming increasingly important. Germanium was first discovered by Clemens Winkler in 1886. See Germanium research below.

Selenium is a Block P, Group 16, Period 4 element. The number of electrons in each of Selenium's shells is 2, 8, 18, 6 and its electronic configuration is [Ar] 3d¹⁰ 4s² 4p⁴. In its elemental form selenium's CAS number is 7782-49-2. The selenium atom has a radius of 116.pm and it's Van der Waals radius is 190.pm. The EPA does not classify selenium as carcinogenic, although selenium sulfide is a probable carcinogen. Selenates and selenites which are compounds of selenium, are highly toxic. Hydrogen selenide gas (SeH2) is the most acutely toxic compound of selenium. Selenium exhibits both photovoltaic action, where light is converted directly into electricity, and photoconductive action, where the electrical resistance decreases with increased illumination. of photocells and exposure meters for photographic use, as well as solar cells. Below its melting point, selenium is a p-type semiconductor and has many uses in electronic and solid-state applications. Selenium is available as metal and compounds with purities from 99% to 99.9999% (ACS grade to ultra-high purity); metals in the form of foil, sputtering target, and rod, and compounds as submicron and nanopowder. Selenium was first discovered by Jons Berzelius in 1817. The origin of the name Selenium comes from the Greek word "Selênê" meaning moon. See selenium research below.