Gallium's boiling point, 2673 K, is nearly nine times higher than its melting point on the absolute scale, the greatest ratio between melting point and boiling point of any element. It is also notable for having one of the largest liquid ranges for a metal, and for having (unlike mercury) a low vapor pressure at high temperatures. Of the four, gallium is the only one that is neither highly reactive (as are rubidium and caesium) nor highly toxic (as is mercury) and can, therefore, be used in metal-in-glass high-temperature thermometers. Gallium is one of the four non-radioactive metals (with caesium, rubidium, and mercury) that are known to be liquid at, or near, normal room temperature. Seeding with a crystal helps to initiate freezing. The liquid metal has a strong tendency to supercool below its melting point/ freezing point: Ga nanoparticles can be kept in the liquid state below 90 K. The melting point of gallium allows it to melt in the human hand, and then solidify if removed. The triple point of gallium, 302.9166 K (29.7666 ☌, 85.5799 ☏), is used by the US National Institute of Standards and Technology (NIST) in preference to the melting point. This melting point (mp) is one of the formal temperature reference points in the International Temperature Scale of 1990 (ITS-90) established by the International Bureau of Weights and Measures (BIPM). The melting point of gallium, at 302.9146 K (29.7646 ☌, 85.5763 ☏), is just above room temperature, and is approximately the same as the average summer daytime temperatures in Earth's mid-latitudes. It readily diffuses into cracks or grain boundaries of some metals such as aluminium, aluminium– zinc alloys and steel, causing extreme loss of strength and ductility called liquid metal embrittlement. Gallium shares the higher-density liquid state with a short list of other materials that includes water, silicon, germanium, bismuth, and plutonium. Gallium liquid expands by 3.10% when it solidifies therefore, it should not be stored in glass or metal containers because the container may rupture when the gallium changes state. Very pure gallium is a silvery blue metal that fractures conchoidally like glass. Gallium(III) behaves in a similar manner to ferric salts in biological systems and has been used in some medical applications, including pharmaceuticals and radiopharmaceuticals.Įlemental gallium is not found in nature, but it is easily obtained by smelting. Gallium has no known natural role in biology. Gallium is considered a technology-critical element by the United States National Library of Medicine and Frontiers Media. Gallium is also used in the production of artificial gadolinium gallium garnet for jewelry. Semiconducting gallium nitride and indium gallium nitride produce blue and violet light-emitting diodes and diode lasers. Gallium arsenide, the primary chemical compound of gallium in electronics, is used in microwave circuits, high-speed switching circuits, and infrared circuits. Gallium is predominantly used in electronics. Elemental gallium is a liquid at temperatures greater than 29.76 ☌ (85.57 ☏), and will melt in a person's hands at normal human body temperature of 37.0 ☌ (98.6 ☏). Gallium does not occur as a free element in nature, but as gallium(III) compounds in trace amounts in zinc ores (such as sphalerite) and in bauxite. An even lower melting point of −19 ☌ (−2 ☏), well below the freezing point of water, is claimed for the alloy galinstan (62–95% gallium, 5–22% indium, and 0–16% tin by weight), but that may be the freezing point with the effect of supercooling. Gallium alloys are used in thermometers as a non-toxic and environmentally friendly alternative to mercury, and can withstand higher temperatures than mercury. The melting point of gallium is used as a temperature reference point. It is also used in semiconductors, as a dopant in semiconductor substrates. Since its discovery in 1875, gallium has widely been used to make alloys with low melting points. If enough force is applied, solid gallium may fracture conchoidally. In its liquid state, it becomes silvery white. Discovered by the French chemist Paul-Émile Lecoq de Boisbaudran in 1875, gallium is in group 13 of the periodic table and is similar to the other metals of the group ( aluminium, indium, and thallium).Įlemental gallium is a soft, silvery metal at standard temperature and pressure. Gallium is a chemical element with the symbol Ga and atomic number 31.
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