A compound can be separated into the individual elements that it is comprised of and an element can separated as far as its individual atoms. An atom represents the smallest possible part of an element that still retains the properties of that element.
Definition of nickel. 1  1 : a silver-white hard malleable ductile metallic element capable of a high polish and resistant to corrosion that is used chiefly in alloys and as a catalyst â see element table. 2  2a (1) : the U.S. 5-cent piece regularly containing 25 percent nickel and 75 percent copper (2) : the Canadian 5-cent pieceb : five cents.
This article is about the U.S. five-cent coin. For its Canadian counterpart, see Nickel (Canadian coin). For United States coins once termed nickels, see Flying Eagle cent, Indian Head cent, and Three-cent nickel. A nickel, in American usage, is a five-cent coin struck by the United States Mint. Composed of 75% copper and 25% nickel, the piece has been issued since 1866. Its diameter is .835 inches (21.21mm) and its thickness is .077 inches (1.95 mm). The silver half dime, equal to five cents, had been issued since the 1790s.