Potassium tarnishes so quickly that it is difficult to see that potassium is actually a shiny metal. This is further evidence that potassium is a more reactive metal than both lithium and sodium.

After the third energy level has 8 electrons, the next electron goes into the fourth level. 4th Period: Potassium and Calcium—Electrons go into the fourth energy level. A small piece of sodium metal ...

when potassium is added to water, the metal melts and floats. It moves around very quickly on the surface of the water. The metal self-ignites, which also ignites the hydrogen gas. This results in ...