What is the unique property executed by : (i)indium (ii)thallium (iii)gallium
Indium--- The name has been given from the indigo blue it shows in a spectroscope. Indium has a low melting point for metals and above its melting point it ignites burning with a violet flame. Bizarrely, the pure metal of indium is described as giving a high-pitched "cry" when bent. This is similar to the sound made by tin or the 'tin cry", however, neither of them is really much like a cry!
It is an excellent choice for cryogenic pumps, high vacuum systems and other unique joining and sealing applications. Indium lends itself to this application due to its ability to conform to many irregular surfaces and its characteristic "stickiness". Indeed, when pure, it sticks very tightly to itself or to other metals. This property makes it useful as a solder - it reduces the melting point of some solders, strengthens others, and prevents some solders from breaking down too easily.
Thallium---The thallium compounds, thallium(I) bromide and thallium(I) iodide crystals have been used as infrared optical materials, because they are harder than other common infrared optics, and because they have transmission at significantly longer wavelengths.
Gallium---Gallium metal expands by 3.1 percent when it solidifies, and therefore storage in either glass or metal containers is avoided, due to the possibility of container rupture with freezing. Gallium shares the higher-density liquid state with only a few materials like silicon, germanium, bismuth, antimony and water. Gallium is a metal that will melt in one's hand. This metal has a strong tendency to supercool below its melting point/freezing point.Seeding with a crystal helps to initiate freezing.
Gallium is one of the metals (with caesium, rubidium, francium and mercury) which are liquid at or near normal room temperature, and can therefore be used in metal-in-glass high-temperature thermometers. It is also notable for having one of the largest liquid ranges for a metal, and (unlike mercury) for having a low vapor pressure at high temperatures.
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