PTL:Gallium
From ChemEd Collaborative
Gallium is a metal in the 4th period and in Group IIIA. Other elements in this group are boron (B), aluminum (Al), indium (In), and thallium (Tl).
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Discovered
Ga was discovered by Lecoq de Boisbaudran in 1875 when he observed two new spectral lines in zinc ores at 403.3 nm and 417.2 nm (in the violet range); in the same year, he isolated the free metal by electrolysis of a solution of gallium hydroxide in KOH. Starting with several hundred kilograms of zinc blende, gathered from the Pyrenees Mountains in South France, he isolated slightly more than one gram of gallium metal. Nowadays, France is the leading refiner of Gallium. A more detailed history taken from Lecoq's own journal entries can be found here.
Name
The name is derived from the Latin word, Gallia, for Gaul and was given to the element by its discoverer, Lecoq de Boisbaudran in honor of his home country of France. Gaul was comprised of France and the regions surrounding it. The symbol Ga is an abbreviation of the name.
Characteristics
The element and its properties were predicted by Mendeleev on the basis of his periodic table of elements. Mendeléev referred to the missing element as eka-aluminum.
Gallium is the only metal, except for mercury, cesium, francium, and rubidium, that can be liquid near room temperatures (its melting point is 29.8°C). It has one of the longest liquid ranges of any metal and has a low vapor pressure even at high temperatures. Therefore it has been used in high-temperature thermometers. More commonly, Galinstan, an alloy of Gallium, Indium, and Tin, is used as it remains a liquid at lower temperatures than water and higher than 1000 degrees Celcius.
Gallium wets glass and porcelain.
Gallium is very reflective, and is used to create liquid mirrors.
Ultra-pure gallium has a silvery appearance with a bluish tinge and the solid metal exhibits a conchoidal fracture similar to glass. (Conchoidal fracture means breaking along lines that look like a cross section of a conch shell; that is, fracturing in curved lines.) This bluish tinge is actually a thin film of Gallium(III) Oxide forming on the surface. The metal expands 3.235% on solidifying (to 6.095 g/cm3), resembling only five other substances (water, Bi, Ge, Si, and Sb) in this regard. Therefore, it should not be stored in glass containers as they may break as the metal solidifies. For this reason, Ga is commonly stored in polyethylene. A video of Gallium in its liquid state can be found here.
Gallium(III) can form complex ions such as [GaCl4] − , [GaBr4] − , and [GaI4] − . Gallium(I) can form ionic compounds with these complex anions, giving the illusion of a Gallium(II) ion. Gallium(II) is not known to exist, unlike Gallium(III) and, though more rare, Gallium(I).
Gallium can seep into the crystal lattice of most metals.
Found
Although widely distributed as Ga-69 and Ga-71, the element does not occur in appreciable quantities, even in its richest ore, germanite. Gallium is found as a trace element in diaspore [AlO(OH)], sphalerite, germanite (Cu26Fe4Ge4S32), bauxite, and coal.
Uses
Gallium has found recent use in doping semiconductors and producing solid-state devices, such as Al-Ga-N and Ga-Ntransistors. Gallium arsenide is capable of converting electricity directly into coherent light and is used in [light-emitting diodes] and is being researched for other optical device applications. Gallium readily alloys with most metals, and has been used as a component in brittle, low-melting alloys. Gallium is also alloyed with Plutonium to stabilize it, particularly applied in atomic bombs.
Gallium alloyed with aluminum rapidly reacts with water to form hydrogen gas. See here. Gallium is also known to stimulate metabolism.
Gallium can be used to create LEDs in the color range from green through ultra-violet and is being researched in night vision goggles.
Gallium, in quantities of tens of tons, is used to detect neutrinos by converting them to electrons.
Gallium, as it is about the same size as iron, can be used to "suffocate" diseases by acting as a competitive inhibitor to iron.
Emission Spectra
This is the emission spectra for Gallium.
