|Atomic mass||140.9077 amu|
Praseodymium was discovered in 1885 when it was separated from an earth called didymium. The earth was thought to contain a mixture of elements, and not a fundamental substance in its own right. Spectroscopic data of didymium yielded two absorption bands, one in the blue region and another in the yellow. When the two elements were separated, the names praseodymia (green didymia) and neodymia (new didymia), which were later modified to conform to standardized nomenclature requiring such metals to have an -ium suffix. The name praseodymium was taken from the Greek meaning "green twin".
Praseodymium is a silvery white, fairly soft, malleable, and ductile metal. It is moderately reactive in air, developing a green oxide coating that falls off to expose fresh metal for further oxidation. The metal is also quite reactive in water. Praseodymium is a rare-earth metal, and is also a member of the lanthanide series.
Praseodymium is used as high-strength alloying agent in the magnesium used in parts of aircraft engines. It is an important alloying agent in steel. About 5% praseodymium is used in the manufacture of flints that are used for creating sparks.
Other applications include using a mixture of praseodymium and neodymium in the manufacture of welder's and glassmaker's goggles because they filter out the yellow light in glass blowing. Certain praseodymium compounds are used as yellow pigments.