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.


Yttrium, symbol Y, silver-white metallic element with an atomic number of 39. Yttrium is one of the transition elements of the periodic table.

Yttrium was isolated by the Swedish chemist Carl Gustav Mosander in 1843. Yttrium metal can be prepared by the reduction of yttrium triflouride with calcium. It oxidizes readily in air to the oxide and dissolves in hot water to form the hydroxide. Yttrium ranks about 29th in abundance of the elements in the earth's crust. Yttrium is found as an oxide in most of the rare earth minerals. It is used extensively in phosphors employed in color television tubes.

Yttrium melts at about 1522° C (about 2772° F), boils at about 3338° C (about 6040° F), and has a specific gravity of 4.47. The atomic weight of yttrium is 88.906. Yttrium is sometimes included among the rare earth elements.