In this video explains metal - Indium. It’s in the third group of the periodic table of chemical elements, below gallium. Indium is unusual because it is the softest metal that you can actually hold in your hands. Lithium is softer that indium, but because of its high activity, lithium will form caustic alkali in hands and oxidize in air. In appearance, indium is shiny and does not tarnish in air. Due to the high softness, indium can be scratched even with a fingernail, you can cut a piece of it off with a regular construction knife.
If you take a piece of indium and a piece of gallium and rub them against each other, then at the point of contact of the two metals a liquid alloy of indium, gallium, will start to form, having a composition of 75.5% of gallium and 24.5% of indium.
The melting point of this alloy is about 15 degrees Celsius and this alloy remains liquid at room temperature. This alloy can very well moisten a glass, forming a beautiful mirror. By the way, in some cars headlights mirrors are covered with indium metal! If you moisten a cotton swab with this alloy, then we would get a metallic pen, with which you can draw conductive lines on the paper. In order to demonstrate you the most interesting property of indium, I decided to cast a thin plate from it.
Pure indium has a melting point of 157 degrees Celsius, it’s possible to easily cast different ingots from this metal. The resulting indium sheet is very soft. Since indium is incredibly soft, you can easily bite a piece of it off.
My teeth are not very strong, so it took me a bit of effort to bite off a piece of indium. Biting indium is not the most pleasant experience, it can be compared to chewing solid tar or soft plastic. Narrow strips of indium make them easier to bite. Also, if you try to bend an indium ingot you can hear a kind of crunching.
This crunch is caused by deformation of crystals inside the metal. The name indium is derived from the beautiful indigo colour, in which it paints the burner flames during combustion in air. Pure indium is used as a component in many alloys, indium compounds are used in electronics, particularly in the manufacture of touch screens.

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