Matter & Energy

Matter is composed of atoms or groups of atoms called molecules. The arrangement of particles in a material depends on the physical state of the substance. In a solid, particles form a compact structure that resists flow. Particles in a liquid have more energy than those in a solid. They can flow past one another, but they remain close. Particles in a gas have the most energy. They move rapidly and are separated from one another by relatively large distances.


Samarium, symbol Sm, hard, brittle, lustrous metallic element. Samarium is one of the rare earth elements in the lanthanide series of the periodic table. The atomic number of samarium is 62.

Samarium was discovered in 1879 by the French chemist P. E. Lecoq de Boisbaudran. The metal ignites in air at about 150° C (about 302° F). Like other rare earth metals, it is found in minerals such as cerite, gadolinite, and samarskite. It is 40th in order of abundance of the elements in the earth's crust. Samarium forms chiefly trivalent compounds; the salts are pale yellow in color. Samarium oxide is used in the control rods of some nuclear reactors.

Samarium melts at about 1074° C (about 1965° F), boils at about 1794° C (about 3261° F), and has a specific gravity of 7.52. The atomic weight of samarium is 150.4.