English: Potassium is an abundant element, which in its pure form is a silvery white, light metal and is very reactive. It explosively reacts with water. When dealing with elemental potassium, painstaking precaution is inevitable. In compounds, potassium is essential to animals and plants, several natural minerals contain it. The rare natural isotope potassium 40, a beta emitter, has a half life of 1.25 billion years. It is responsible for the largest part of the normal radioactive exposure.