Nickel
. 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. II PROPERTIES 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. OCCURRENCE Nickel occurs as a metal in meteor