Potassium is a chemical element with the symbol K, and atomic number 19. It was first isolated from potash, the ashes of plants, and it takes the name from the mineral, potassium is one of the alkali metals, and all of the alkali metals has a single valence electron, in the outer electron shell, which can be easily removed to create a cation. It occurs naturally in ionic salts, and pure potassium, is a soft white, alkali metal that oxidizes in the air and reacts vigorously in water, giving it enough heat to ignite hydrogen emitted in the reaction, and burning it with a light purple flame, and it is found dissolved in sea water, and it is part of many minerals. It is chemically similar to sodium, the previous element on group 1 of the periodic table and they have a similar ionization energy, which can combine with different elements with the same anions, to make the same salts, and it was proven in 1807 using electrolysis. Naturally occurring potassium comes in 3 isotopes, and potassium-40 is the most familiar kind, and potassium-40 does occur in bananas though the dose is not enough to kill you.
Potassium is also essential to human health, as it promotes muscle relaxation, without it you'd suffer from rhabdomyolysis, along with potentially weakening muscle problems later in life, and this is known as hypokalemia. Potassium can also be used for industrial and agricultural usage, such as in fertilizer, and in medicine as a supplement.