What is Potassium?
{{Infobox potassium}} [[File:Potassium.JPG|thumb|Potassium metal]] '''Potassium''' is a [[chemical element]] in the [[periodic table]]. It has the [[symbol]] '''K'''. This symbol is taken from the [[Latin language|Latin]] word ''kalium''. Potassium's [[atomic number]] is 19. It has 19 [[proton]]s and [[electrons]]. Potassium is not found as an element in nature, because it is so reactive. Potassium has two stable [[isotope]]s, with 20 or 22 [[neutron]]s. Its [[atomic mass]] is 39.098. The unstable isotope with 21 neutrons is one of the most common [[radioactive]] materials. == Properties == === Physical properties === Potassium is a soft gray [[metal]]. It can be cut easily with a knife. Its melting point is 63 degrees Celsius (145.4 degrees Fahrenheit). It melts at a very low temperature. It is an [[alkali metal]]. It is the second lightest metal, after [[lithium]]. === Chemical properties === [[File:Potassium water 20.theora.ogv|250px|thumb|alt=A piece of potassium metal is dropped into a clear container containing water and slides around, burning with a bright pinkish or lilac flame for a short time until finishing with a pop and splash.|A reaction of potassium metal with water. [[Hydrogen]] is liberated. The pink or lilac flame comes from burning potassium vapor. Strongly [[alkaline]] potassium hydroxide is formed in solution.<ref>{{cite web |url=http://www.chemeddl.org/collections/ptl/PTL/elements/K/images/fig1.html |title=Potassium |author= |publisher= |accessdate=13 October 2010 }}{{Dead link|date=January 2021 |bot=InternetArchiveBot |fix-attempted=yes }}</ref>]] Potassium reacts in many chemical [[Chemical reaction|reactions]] similar to [[sodium]] and other alkali metals. It [[tarnish]]es in air to produce a whitish [[oxidation|oxidized]] layer on the surface. This is why it is stored in [[oil]]. It also reacts very fast with water, which is another reason for its storage in oil. The hydrogen produced during its reaction with water can burst into flames when a large amount of potassium is added to wa