Potassium is an element, the 19th element of the periodic table. Potassium is so highly reactive that in nature, it's never found in pure form. Pure elemental potassium reacts violently with water. Does this Spark an idea?
Although potassium isn't found in pure form in nature, chemists can isolate it in the lab through electrolysis. Pure potassium must be stored and handled carefully, because potassium, like the other alkali metals (group 1 elements), has a low ionization energy and is extremely reactive. When potassium comes in contact with water, potassium atoms are oxidized to form potassium hydroxide; the reaction releases hydrogen gas and a great deal of heat, igniting the hydrogen and starting a fire.
In nature, potassium is found in ionic compounds like potassium chloride. Potassium compounds, like those of other group 1 alkali metals, are water soluble as a general rule, meaning they dissolve well in water. When an ionic compound like potassium chloride or potassium nitrate dissolves in water, it dissociates into potassium ions (K+) and anions (negatively charged ions). In water, potassium ions are colorless.
Potassium is important for life. Many vital physiological processes in plants and animals make use of potassium ions in water, often by pumping potassium ions one way across the cell membrane and pumping sodium ions the other way to help regulate osmotic pressure (pressure caused by water diffusing across the membrane) and/or create an electrochemical gradient. Potassium is one of the important nutrients that plants take up from the soil.