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 Samarium, Sm, Lanthanide. Samarium is one of the less common of the rare earth elements, being on the one hand much less abundant than the other elements of the cerium group, and on the other hand much more abundant than europium, terbium, and thulium. It is about as plentiful as gadolinium. Samarium is a yellow metal of density 7. The metal quickly tarnishes in the air. Extracted by Mosander from ceria earth. The samarskite mineral was named.

Element Lanthanum, La, Lanthanide. Lanthanum is a tin-white metal of density 6. It is malleable, but not ductile. Measurements made with material of doubtful purity indicate that lanthanum is feebly paramagnetic, but this is questionable. 923 and its heat of formation 97. it resembles the corresponding cerium compound.

Element Actinium, Ac, Actinide or Actinoid. After which the latter name was confirmed. Is a member of actinide. Isotopes with mass numbers from 221 to 230 are known. The most long-lived of them is. However, comparing with other elements actinium abundance. Is extremely small, 6x10.

Element Caesium, Cs, Alkali Metal. Had undoubtedly been examined before, but had been mistaken by C. Plattner for potassium salts, meanwhile it was consisting of hydrous caesium. Pisani revealed it on the analysis of pollux in 1864.