Rubidium (Ru)

Rubidium ([Kr]5s¹) (CAS 7440-17-7) is a soft, silvery-white metal belonging to the alkali group. It is second in the categories of most electropositive and most alkaline elements Rubidium forms amalgams with mercury and alloys with gold, cesium, sodium, and potassium. It is highly reactive; igniting spontaneously in air and reacting vigorously in water. Rubidium has a high heat capacity and heat transfer coefficient.