Atomic mass- 140.9
Atomic number- 59
It is also a metal and is solid at room temperature with a density of 6.77 grams per cubic centimeter.
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Praseodymium was discovered in 1885 by Carl Auer von Welsbach by crystalizing didymium and observing two different colored crystals that were formed: pink crystals which are neodymium, and green crystals which are praseodymium. These new elements replaced didymium on the periodic table.
"Praseodymium Element Facts / Chemistry." Chemicool. N.p., n.d. Web. 28 Oct. 2014.
Knapp, Brian J., and David Woodroffe. Potassium to Zirconium. Danbury, CT: Grolier Educational, 2002. Print.