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.


Nickel, symbol Ni, silvery white, magnetic metallic element used chiefly in making alloys. Nickel is one of the transition elements of the periodic table (see Periodic Law). The atomic number of nickel is 28.

Nickel was used as coinage in nickel-copper alloys for several thousand years, but was not recognized as an elemental substance until 1751 when the Swedish chemist Baron Axel Frederic Cronstedt isolated the metal from niccolite ore.


Nickel is a hard, malleable, ductile metal, capable of taking a high polish. It is magnetic below 345° C (653° F). It exists in five stable isotopic forms. Metallic nickel is not very active chemically. It is soluble in dilute nitric acid and becomes passive (nonreactive) in concentrated nitric acid; it does not react with alkalies. Nickel melts at about 1455° C (about 2651° F), boils at about 2730° C (about 4946° F), and has a specific gravity of 8.9. The atomic weight of nickel is 58.69.


Nickel occurs as a metal in meteors. Combined with other elements, it occurs in minerals such as garnierite, millerite, niccolite, pentlandite, and pyrrhotite; the latter two minerals are the principal ores of nickel. Nickel ranks about 22nd in natural abundance among elements in crustal rock.

Nickel ores usually contain impurities, chief among which is copper. Sulfide ores, such as pentlandite and nickeliferous pyrrhotite, are usually smelted in a blast furnace and shipped in the form of a matte of copper and nickel sulfide to refineries, where the nickel is removed by various processes.


Nickel is used as a protective and ornamental coating for metals, particularly iron and steel, that are susceptible to corrosion. The nickel plate is deposited by electrolysis in a nickel solution. Finely divided nickel absorbs 17 times its own volume of hydrogen and is used as a catalyst in many processes, including the hydrogenation of oils.

Nickel is used chiefly in the form of alloys. It imparts great strength and corrosion resistance to steel. Nickel steel, containing about 2 to 4 percent nickel, is used in automobile parts such as axles, crankshafts, gears, valves, and rods; in machine parts; and in armor plate. Some of the most important nickel-containing alloys are German silver, Invar, Monel metal, Nichrome, and Permalloy. The nickel coins used for currency are an alloy of 25 percent nickel and 75 percent copper. Nickel is also a key component of nickel-cadmium batteries.