Rubidium is located on the fifth row of the first column in the periodic table of elements. Its appearance is silvery white with a melting point of 39 degrees Celsius. Rubidium continues the pattern in the reactivity in the alkali metals by being even more reactive than Potassium.  It is stored in sealed ampules filled either with Argon or a vacuum. Rubidium is also a very soft metal. Rubidium has 2 naturally occurring isotopes though many more are produced artificially for many purposes. Rubidium 85 is the most common naturally occurring isotope of Rubidium accounting for 75% of all Rubidium. Rubidium 87 is radioactive with a half-life of 50 billion years. It makes up about 25% of naturally occurring Rubidium.

Rubidium's uses are much more limited due to its extreme reactivity. however, the decay of Rubidium 87 to Strontium 87 is used to age old rocks. The artificial isotope Rubidium 82 has been used to stimulate the flow of Potassium through the body, and also to locate brain tumors.