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.


Antimony, symbol Sb, bluish-white, brittle, semimetalic element. The atomic number of antimony is 51; the element is in group 15 (or Va) of the periodic table.

Antimony's compounds were known in ancient times, and the element was probably discovered by the German alchemist Basil Valentine about 1450. It was certainly known by about 1600, but was confused with other elements, such as bismuth, tin, and lead. Antimony generally shows the properties of a metal, but sometimes shows those of a nonmetal. It exists in several distinctly different physical forms, the most common of which is metallic in appearance.

Antimony ranks about 64th in natural abundance among the elements in crustal rock. The atomic weight of antimony is 121.75; it melts at about 630° C (about 1166° F), boils at about 1750° C (about 3182° F), and has a specific gravity of 6.7. It occasionally occurs as a free element, usually associated with silver, arsenic, or bismuth. It crystallizes in the hexagonal system (see Crystal), but crystals are rarely found. It has a hardness of 3. The principal ore of antimony is stibnite, a sulfide of antimony, which is mined in China, France, Italy, Japan, Mexico, and, on a small scale, in the western United States. Considerable amounts of antimony are produced as a by-product in the refining of ores of copper and lead.

Liquid antimony has the exceptional property, when cooling, of expanding as it solidifies (water is one of the few other substances with this same property). It will thus fill in the crevices of a mold and yield castings of exceptionally sharp outlines. For this reason, it is used in making type metal; it is also a constituent of many other alloys, such as Britannia metal, pewter, Babbitt metal and antimonial lead.

Among important compounds of antimony are tartar emetic, a double tartrate of antimony and potassium used as a medicinal agent; red antimony sulfide, used on safety matches and in vulcanizing rubber; glass of antimony, a mixture of antimony sulfide and oxide, used as a yellow pigment in glass and porcelain; and butter of antimony, antimony trichloride, used for bronzing steel, as a mordant in dyeing, and as a caustic in medicine.