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.


Bismuth, symbol Bi, rare metallic element that has a pinkish tinge. The atomic number of bismuth is 83; it is in group 15 (or Va) of the periodic table (see Periodic Law).

Bismuth was known in ancient times, but until the middle of the 18th century, it was confused with lead, tin, and zinc. Ranking about 73rd in natural abundance among the elements in the earth's crust, it is about as rare as silver. Most industrial bismuth is obtained as a by-product.

Chemically, bismuth is a typical metal. In compounds it has valences of +3 or +5, the compounds of trivalent bismuth being more stable. There are several nitrates, notably bismuth nitrate or bismuth trinitrate; and bismuth nitrate pentahydrate. The latter form decomposes into basic bismuth nitrate. Basic bismuth nitrate is also known as bismuth oxynitrate, or bismuthyl nitrate, and may be used in medicine and cosmetics. Other names for basic bismuth nitrate are pearl white and Spanish white.

Bismuth expands on solidifying; this unusual property makes it useful for castings. Some of its alloys have unusually low melting points. One of the most strongly diamagnetic (difficult to magnetize) of all substances, bismuth tends to turn at right angles to a magnetic field. It is a poor conductor of heat and electricity, and its electrical resistance is further increased in a magnetic field; because of this property, it is used in instruments for measuring the strength of such fields. Bismuth is opaque to X rays and can be used in fluoroscopy.

Among the nonradioactive elements, bismuth has the highest atomic weight (208.98) and atomic number. It melts at 271° C (520° F), boils at 1560° C (2840° F), and has a specific gravity of 9.8.