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.


Neodymium, symbol Nd, silvery metallic element with an atomic number of 60. Neodymium is one of the rare earth elements in the lanthanide series of the periodic table. Neodymium was isolated in 1885 by the Austrian chemist Baron Carl Auer von Welsbach, who separated it from praseodymium. Neodymium and praseodymium had previously been regarded as a single element, called didymium. Neodymium ranks 27th in order of abundance of the elements in the earth's crust. It forms trivalent salts, which are rose-red or reddish-violet in color. The metal's oxide, Nd2O3, is used in the glass of color-television tubes to increase contrast, and in lasers.

Neodymium melts at about 1021° C (about 1870° F), boils at about 3074° C (about 5565° F), and has a specific gravity of 7.01. The atomic weight of neodymium is 144.24.