Gadolinium, << `gad` uh LIHN ee um, >> is a silver-white metal of the lanthanide group of chemical elements (see Lanthanide ). It was discovered in 1880 by the Swiss scientist Jean de Marignac. Marignac named the element for Johan Gadolin, a Finnish chemist.
Gadolinium is found with other lanthanides in the mineral gadolinite. It is sometimes used in control rods of nuclear reactors to absorb neutrons produced inside the reactor. Gadolinium’s chemical symbol is Gd. The element’s atomic number (number of protons in its nucleus) is 64. Its relative atomic mass is 157.25. An element’s relative atomic mass equals its mass (amount of matter) divided by 1/12 of the mass of carbon 12, the most abundant form of carbon. Gadolinium is strongly magnetic at room temperature but loses its magnetism when heated slightly. It melts at 1313 °C and boils at 3273 °C. Its density is 7.886 grams per cubic centimeter at 25 °C. For information on the position of gadolinium on the periodic table, see the article Periodic table .
