Element Barium, Ba, Alkaline Earth Metal. Has the combining weight 137. 4, and occurs naturally as sulphate and carbonate. Metallic barium is of a white colour, melts at a red heat, and reacts more energetically with water than strontium or calcium. We have here, therefore, a repetition of the same state of affairs as in the group of alkali metals, viz. the action with oxygen and oxygen compounds is more energetic the higher the combining weight of the metal. Barium forms only the divalent ion Ba.

Element Francium, Fr, Alkali Metal. By Perey for her native country. Does not have stable isotopes. 27 known radioactive isotopes have mass numbers from 202 to 229.

Element Radium, Ra, Alkaline Earth Metal. Isotopes may be found in nature. It becomes possible because of existence of three radioactive series in which radium isotopes.

Element Rubidium, Rb, Alkali Metal. During their investigations they became interested in the mineral lepidolite. The processed 150 kg and, as a result, separated double potassium, caesium and rubidium. The crustal abundance of rubidium.

Element Strontium, Sr, Alkaline Earth Metal. Strontium forms only the divalent ion Sr. Whose solutions are colourless, and whose heat of formation is 501 kj. A very rare mineral, which before that could be found only in a couple of collections, named after the village of Strontian, Lochaber, Scotland. A mineral consisting of barium sulphate. He called the mineral strontianite.