Nickel

Nickel is a transition metal with the symbol Ni and atomic number 28. It is well-known as a coinage material due to its corrosion resistance, and is often used to plate objects. In solution, it has extensive coordination chemistry, and some interesting redox chemistry which is not commonly seen.

Properties

Physical properties

Nickel is a silvery-white metal that has a slight yellowish tinge. It is one of four elements that is ferromagnetic at or near room temperature (iron, cobalt, and gadolinium being the others). Its Curie temperature is 355 °C, which causes the metal to reversibly become paramagnetic. It is hard yet ductile.

Chemical properties

Much of nickel's chemical resistance owes to its passivation in air. It will also passivate in the presence of fluorine, making it an ideal material for handling and storing the gas. It will dissolve only slowly in hydrochloric and sulfuric acids. In concentrated nitric acid, nickel will not dissolve, but it will dissolve in dilute nitric acid.

Nickel(II) compounds form a hexaaqua complex in water with the formula [Ni(H₂O)₆]²⁺ and coordinate to many different ligands, including chloride, ammonia, and ethylenediamine. These complexes can be hexacoordinate, tetragonal, or square planar, with square planar complexes such as tetrachloronickelate being diamagnetic rather than paramagnetic.

Availability

Nickel is present as the main material in older Canadian nickels. It is also present in US nickels, dimes, and quarters, however, the majority of the metal is copper, with nickel making up anywhere from 9% to 25% of the coin. Destroying coins is illegal however, and heavy fines exist everywhere for breaking this law.

Nickel strips for electroplating can be bought from United Nuclear.

Projects

• Nickel plating
• Coordination complexes
• Building a battery

Safety

Nickel compounds are known to be carcinogens, and are grouped as class 1. Nickel metal is grouped as class 2B (it is a suspected carcinogen). However, it is not regulated by OSHA.

Some people are allergic to nickel metal and develop an itch or rash when exposed to it (contact dermatitis). If this occurs, wear gloves when handling the metal.