Page 6 - Curriculum Visions Dynamic Book

Praseodymium (Pr)
Key facts...
Name: praseodymium
Symbol: Pr
Atomic number: 59
Atomic weight: 140.9
Position in Periodic Table: inner transition
metal; period 6 (lanthanide series) State at room temperature: solid Colour: silvery
Density of solid: 6.77 g/cc
Melting point: 931°C
Boiling point: 3,212°C
Origin of name: from the Greek words
prasios and didymos, meaning green twin Shell pattern of electrons: 2–8–18–21–8–2
Element 59.This silvery-coloured, soft and malleable metal is one of the rare-earth metals (lanthanide series) in the Periodic Table. It reacts slowly in air, being more resistant
to corrosion in air than europium, lanthanum, cerium, or neodymium, but it does develop a green oxide coating that chips off.To prevent this, it has to be kept under oil or coated in plastic.
Discovery
The discovery was complicated and followed a sequence of isolations. In 1841 Carl Gustaf Mosander extracted the rare earth didymia from lanthana; in 1879 Lecoq de Boisbaudran isolated a new rare earth, samaria, from didymia obtained from the mineral samarskite.Then in Austria in 1885 Carl Auer von Welsbach, using a sample of the mineral samarskite, found two elements: praseodymium and neodymium. Previously, the mixture of elements had been thought of as a
single element and called didymium. Praseodymium is the 37th most abundant element on the Earth’s surface.
Technology
It is used as an alloy in high-strength metals. It is also 50% of misch metal, which makes lighter flints, and goes into glass for welder’s goggles because it strongly absorbs harmful light from the welding process. It is also used in carbon arc lighting.The colourless salts of praseodymium add a very intense and clean yellow colour to glass.
Geology
It is not found as a native element, but in minerals such as monazite (a phosphate) and bastnasite (a carbonate).
Biology
It is not found in living things.
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