Nickel Ni

Discovery

Alloys containing nickel were used long before the element was known. In China a copper–nickel–zinc alloy called paktong (baitong, 'white copper') was made for centuries, and some ancient coins contain significant amounts of nickel.

German miners of the seventeenth century knew a reddish ore that looked like copper ore but yielded no copper when smelted. They called it Kupfernickel, roughly 'copper-demon', blaming a mischievous spirit. In 1751 the Swedish mineralogist Axel Fredrik Cronstedt, while trying to extract copper from this mineral (now called nickeline, nickel arsenide), obtained instead a hard white metal and announced it as a new element. Some chemists doubted it was not merely a mixture of known metals until Torbern Bergman prepared purer nickel in 1775 and confirmed Cronstedt's conclusion.

Origin of the name

Cronstedt shortened Kupfernickel to nickel. Nickel was a German word for a goblin or rascal, and the name expressed the miners' frustration with an ore that seemed to cheat them. The symbol is Ni.

Main uses

• Stainless steel: roughly two thirds of nickel is used to make austenitic stainless steels, which are tough and corrosion-resistant.
• Batteries: nickel-rich cathodes give lithium-ion batteries high energy density, and nickel–metal hydride cells power many hybrid cars.
• Superalloys: nickel-based alloys form the turbine blades of jet engines, keeping their strength close to their melting point.
• Plating and coins: nickel plating protects and decorates metal parts, and cupronickel is used for coins in many countries.
• Special alloys and catalysts: Invar, an iron–nickel alloy, barely expands when heated; finely divided nickel catalyses the hydrogenation of oils.

Isotopes

Nickel has five stable isotopes: nickel-58 (about 68 percent), nickel-60 (about 26 percent), nickel-61, nickel-62 and nickel-64. Nickel-62 has the highest binding energy per nucleon of any known nucleus. The radioactive nickel-63, with a half-life of about 100 years, is used in electron capture detectors for gas chromatography and in long-life betavoltaic batteries. Nickel-56, made in supernova explosions, decays through cobalt-56 to iron-56, and this chain powers the glow of supernovae for months.

In everyday life

Nickel is the most common cause of contact allergy. Earrings, watch buckles, belt buckles and jeans buttons that release nickel can cause itchy rashes, which is why the European Union limits nickel release from items that touch the skin.

Nickel may be a trace nutrient for some organisms, but no essential role in humans has been proven. Nickel carbonyl, a volatile compound used in refining, is extremely toxic.