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.
Nickel is a silver-colored metal found naturally in the environment. Small amounts of nickel are also found in many foods, including certain grains, fruits, and vegetables. A nickel allergy is an adverse immune response that occurs when someone comes into contact with a product containing nickel.