Page 7 - Curriculum Visions Dynamic Book

Promethium (Pm)
Element 61.This radioactive metal
is one of the rare-earth metals (lanthanides) in the Periodic Table. It is the only rare earth that is not found in nature. Promethium compounds glow (luminesce) pale blue in the dark because of their radioactivity.
Discovery
Promethium was predicted in 1902, but was first identified in 1926.At that time the names illinium and florentium were suggested. It
was discovered in 1945 by J. A. Marinsky, L. E. Glendenin and C.D. Coryell at Oak Ridge, Tennessee.They achieved this by fission of uranium and by neutron bombardment of neodymium.They then named the new element promethium. It was the last of the rare-earth elements to be discovered.
Technology
It is used in very small specialised atomic batteries. Promethium absorbs light and converts it into an electric current. It can also be a beta source for thickness gauges. However, its scarcity prevents it from being widely applied.
Geology
It does not occur in the environment. Despite many searches for it, it seems that promethium does not exist in the Earth’s crust. It has, however, been identified in the stars. Promethium has been prepared from nuclear reactor wastes.
Biology
It is not found in living things. However, because of its radioactivity, it is dangerous to handle.
Key facts...
Name: promethium
Symbol: Pm
Atomic number: 61
Atomic weight: 145
Position in Periodic Table: inner transition
metal; period 6 (lanthanide series) State at room temperature: solid Colour: metallic
Density of solid: 7.26 g/cc
Melting point: 1,080°C
Boiling point: 2,460°C
Origin of name: named after Prometheus
in Greek mythology, who stole fire from
the gods
Shell pattern of electrons: 2–8–18–23–8–2
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