![]() ![]() When an atom gains one or more electrons, forming an anion, the added. For b) 'S'(2-) has a larger radius than the neutral S atom. This is because the loss of electrons reduces the shielding effect between the electrons and the nucleus, so the attraction of the nucleus for the electrons is greater, reducing the radius. Its toxicity appears to be of a low order, but should be handled with care until more data is available. For a) the neutral Ca atom has a larger radius than the 'Ca'(2+) ion. Gallium readily alloys with most metals, and has been used as a component in low-melting alloys. Gallium arsenide is capable of converting electricity directly into coherent light. Iron atoms are significantly smaller than calcium atoms. Magnesium gallate containing divalent impurities, such as Mn +2, is finding use in commercial ultraviolet-activated powder phosphors. The relative atomic mass of calcium is 40, but the RAM of iron is 56, for example. It is widely used in doping semiconductors and producing solid-state devices such as transistors. Gallium wets glass or porcelain and forms a brilliant mirror when it is painted on glass. High-purity gallium is attacked only slowly by mineral acids. The metal expands 3.1 percent on solidifying therefore, it should not be stored in glass or metal containers, because they may break as the metal solidifies. Ultra-pure gallium has a beautiful, silvery appearance, and the solid metal exhibits a conchoidal fracture similar to glass. Therefore, seeding may be necessary to initiate solidification. There is a strong tendency for gallium to supercool below its freezing point. It has one of the longest liquid ranges of any metal and has a low vapor pressure even at high temperatures. It is one of four metals - mercury, cesium, and rubidium - which can be liquid near room temperature and, thus, can be used in high-temperature thermometers. Some flue dusts from burning coal have been shown to contain as much 1.5 percent gallium. Gallium is often found as a trace element in diaspore, sphalerite, germanite, bauxite, and coal. Predicted and described by Mendeleev as ekaaluminum, and discovered spectroscopically by Lecoq de Boisbaudran in 1875, who in the same year obtained the free metal by electrolysis of a solution of the hydroxide in KOH. Gallium metal is silver-white and melts at approximately body temperature (Wikipedia image).ģ, 2, 1, −1, −2, −4, −5 (an amphoteric oxide)įrom the Latin word Gallia, France also from Latin, gallus, a translation of "Lecoq," a cock.
0 Comments
Leave a Reply. |