Nickel – facts and properties
- Symbol
- Ni
- Atomic number
- 28
- Atomic mass
- 58.693 u
- Period
- 4
- Group
- 10
- Category
- transition metal
- Electron configuration
- [Ar] 3d⁸ 4s²
- Electronegativity
- 1.91
- Atomic radius
- 149 pm
- Valence electrons
- 10
- State at standard conditions
- solid
- Melting point
- 1455 °C
- Boiling point
- 2913 °C
- Density
- 8.912 g/cm³
- Discovered
- 1751
Nickel is a silvery-white, shiny metal with atomic number 28. It is found in stainless steel, in coins and in rechargeable batteries. Many people know it best from nickel allergy, which shows up with costume jewellery, belt buckles and watch straps. Its name is a leftover from miners' language and recalls a trick that the ore once played on them.
Position in the periodic table
Occurrence and extraction
Nickel is less common than iron in the Earth's crust, but plentiful in the core, which consists mostly of an iron-nickel alloy. Iron meteorites also often contain several percent nickel. It is hardly ever found native at the surface. There are two main types of deposit. In sulfide ores such as pentlandite, for example at Sudbury in Canada, nickel is bound to sulfur. In laterite ores, which form by tropical weathering, it occurs in oxide and silicate minerals. A large part of today's nickel comes from such ores, above all from Indonesia and the Philippines.
Miners in the Ore Mountains of Germany found a reddish-brown ore that looked like copper ore but gave no copper when smelted. They blamed a mine spirit called Nickel and named the mineral kupfernickel, or false copper. The Swedish chemist Axel Fredrik Cronstedt examined it and found a new metal in 1751, which he called nickel.
To extract it, sulfide ores are roasted and smelted to a nickel matte, which is purified further, usually by electrolysis at the end. In the Mond process the metal is purified by way of the very poisonous nickel tetracarbonyl, a method for industry and not for a school laboratory.
Properties and reactions
Nickel is in period 4 and group 10, and its electron configuration is [Ar] 3d⁸ 4s². Its electronegativity is 1.91. The metal has a density of 8.912 g/cm³, melts at 1455 °C and boils at 2913 °C. It is hard, tough and takes a good polish, with a slight golden shimmer. Like iron and cobalt, nickel is ferromagnetic.
Chemically, nickel is fairly resistant. In air it forms a thin, dense oxide layer that protects it from further corrosion. It dissolves slowly in dilute acids and not at all in alkalis. In almost all of its compounds it is nickel(II). Solutions of nickel(II) salts are green, because complexes with six water molecules form. Finely divided nickel is an excellent catalyst for hydrogenation, that is, for adding hydrogen to carbon compounds.
Nickel and its compounds are not harmless. Many nickel compounds, such as soluble nickel salts, are regarded as carcinogenic when inhaled, and nickel metal dust as a suspected carcinogen. You should never experiment with nickel salts yourself. In addition, nickel causes contact allergy more often than any other metal.
Uses in everyday life and technology
About two thirds of nickel goes into making stainless steel. Ordinary stainless steel contains chromium and nickel. The nickel makes it tough, easy to shape and resistant to many acids, which is why sinks, cutlery and containers in the food industry are made of it. Nickel-based alloys withstand high temperatures and are used in turbines and jet engines. The alloy Invar, made of iron and nickel, hardly expands when heated and is used for measuring instruments.
Coins are often made of nickel or of copper-nickel alloys, because these are hard, resistant to corrosion and difficult to counterfeit. The one- and two-euro coins also consist of copper-nickel and nickel-brass. Thin layers of nickel serve as a coating on taps, tools and keys and are applied by electroplating.
Batteries are important too. In nickel-metal hydride cells, such as many rechargeable AA batteries, nickel hydroxide reacts at one electrode. Many lithium-ion batteries for electric cars also contain nickel in the cathode, because it raises the energy density. In margarine making, a nickel catalyst hydrogenates liquid vegetable oils into solid fats.
Nickel allergy is a hypersensitivity of the skin. Sweat dissolves small amounts of nickel ions from objects containing nickel, and these can cause itching and rashes. The EU therefore limits how much nickel jewellery and piercings may release onto the skin. People who are affected should choose titanium, nickel-free stainless steel, plastic or nickel-free gold; white gold often contains nickel.
Molecules containing this element
- Nickel(II) oxide NiO
- Nickel(II) hydroxide Ni(OH)2
- Nickel(II) sulfate NiSO4
Quick question
What is the atomic number of nickel (Ni)?
FAQ
Why does nickel cause allergies?
Sweat dissolves nickel ions from jewellery, buttons or belt buckles. In some people the immune system recognises them as foreign and reacts with inflammation of the skin: redness, itching and a rash. The allergy usually lasts for life.
Is nickel magnetic?
Yes. Like iron and cobalt, nickel is a ferromagnetic metal and is attracted by magnets. With coins and stainless steel it depends on the alloy: stainless steel containing nickel is often only weakly magnetic or not magnetic at all.
Where does the name nickel come from?
From the miners of the Ore Mountains in Germany. They found an ore that looked like copper ore but gave no copper, and they blamed a mine spirit called Nickel, a kind of goblin. They called the ore kupfernickel. The chemist Cronstedt later took the name of the metal from it.