Average mass of an atom in unified atomic mass units (1 u is 1/12 of the mass of a carbon-12 atom). Accounts for the natural mix of the element’s isotopes.
Number of the vertical column, 1 to 18 in IUPAC numbering. Elements in a group share the same outer-shell layout, so their properties are alike.
Number of the horizontal row. Usually equal to the number of electron shells in the atom; palladium is the exception, with four shells in period 5.
The subshell (s, p, d or f) that receives the last electrons in the usual filling order; it divides the table into four blocks. Real atoms sometimes differ: lanthanum starts the f-block but has no f electrons.
[Ar] 4s² 3d⁸
How electrons are arranged in subshells. The bracket stands for the previous noble gas; the superscript is the number of electrons in a subshell.
2, 8, 16, 2
Number of electrons in each shell, from the nucleus outwards.
1,455 °C (1,728 K)
Temperature at which the solid turns liquid at standard pressure. Helium, carbon and arsenic do not melt at normal pressure: helium needs about 25 atm, carbon and arsenic turn straight into vapour.
2,913 °C (3,186 K)
Temperature at which the liquid boils at standard pressure. For carbon and arsenic, the temperature at which the solid turns straight into vapour (sublimation).
8.912 g/cm³
Mass of one cubic centimetre of the substance. For gases, at 0 °C and standard pressure.
1.91 Pauling
How strongly an atom pulls electrons towards itself in a chemical bond. On the Pauling scale it runs from 0.79 for caesium to 3.98 for fluorine.
7.64 eV
Energy needed to remove the most loosely bound electron from an atom. The lower it is, the more easily the element gives up an electron, which is typical of metals.
1.157 eV
Energy released when a neutral atom gains an electron. Highest for the halogens. Noble gases, nitrogen and some metals form no stable negative ion.
124 pm
Half the length of a single covalent bond between two atoms of the element. It shows the size of an atom inside a molecule or crystal: 76 pm for carbon, 132 pm for iron.
+3, +2
Charges the atom would have in its compounds if all its bonds were ionic; the main ones are listed.
Nickel (Ni) is a chemical element with atomic number 28. It sits in group 10 and period 4 of the periodic table, in the d-block. It is a transition metal. At room temperature it is a solid. Its standard atomic weight is 58.693.
Origin of the name
Miners in medieval Germany found an ore that looked just like copper ore, yet no copper could be got out of it. They blamed Nickel, a mischievous sprite of the mines, and called the ore Kupfernickel, ‘Nickel’s copper’. In 1751 the Swedish chemist Axel Fredrik Cronstedt tried to extract copper from it and instead obtained a white metal, which he named nickel after the sprite.
Where is nickel found?
Nickel is mined from sulfide ores such as pentlandite and from nickel-bearing laterite soils. Indonesia is now the largest producer; the Sudbury basin in Canada is one of the most famous deposits. Iron meteorites are alloys of iron and nickel, and the Earth’s core is believed to be iron mixed with nickel.
What is nickel used for?
Most nickel goes into stainless steel. Nickel plating protects other metals, nickel goes into coins and rechargeable batteries, and finely divided nickel is the catalyst that hardens vegetable oils. Copper-nickel pipes resist sea water in desalination plants.
Interesting facts
In the United States and Canada the five-cent coin is simply called a nickel.
Some people are allergic to nickel: touching nickel-plated objects gives them an itchy skin rash.
Long before nickel was known as an element, the Chinese made baitong, ‘white copper’, a silvery alloy containing copper and nickel.