Rare Earth Elements
Lanthanide Series
Name: Promethium
Symbol: Pm
Atomic Weight: 144.9127
Atomic Number: 61
Element Classification: Rare Earth Elements
Discovered By: J.A. Marinsky, L.E. Glendenin, C.D. Coryell
Discovery Date: 1945 (United States)
Name Origin:Named for the Greek god, Prometheus.
Name: Samarium
Symbol: Sm
Atomic Weight: 150.36
Atomic Number: 62
Element Classification: Rare Earth Elements
Discovered By: Jean Charles Galissard de Marignac
Discovery Date: 1853 (France)
Name Origin:Named after the mineral samarskite.
Name: Europium
Symbol: Eu
Atomic Weight: 151.965
Atomic Number: 63
Element Classification: Rare Earth Elements
Discovered By: Eugene-Antole Demarcay
Discovery Date: 1901 (France)
Name Origin:Named for the continent of Europe.
Name: Gadolinium
Symbol: Gd
Atomic Weight: 157.25
Atomic Number: 64
Element Classification: Rare Earth Elements
Discovered By: Jean de Marignac
Discovery Date: 1880 (Switzerland)
Name Origin:Named after the mineral gadolinite.
Name: Terbium
Symbol: Tb
Atomic Weight: 158.92534
Atomic Number: 65
Element Classification: Rare Earth Elements
Discovered By: Carl Mosander
Discovery Date: 1843 (Sweden)
Name Origin:Named after Ytterby, a village in Sweden.
Name: Dysprosium
Symbol: Dy
Atomic Weight: 162.50
Atomic Number: 66
Element Classification: Rare Earth Elements
Discovered By: Paul-Emile Lecoq de Boisbaudran
Discovery Date: 1886 (France)
Name Origin:Greek: dysprositos (hard to get at).
Name: Holmium
Symbol: Ho
Atomic Weight: 164.93032
Atomic Number: 67
Element Classification: Rare Earth Elements
Discovered By: J.L. Soret
Discovery Date: 1878 (Switzerland)
Name Origin:Holmia, the Latinized name for Stockholm, Sweden.
Name: Erbium
Symbol: Er
Atomic Weight: 167.26
Atomic Number: 68
Element Classification: Rare Earth Elements
Discovered By: Carl Mosander
Discovery Date: 1843 (Sweden)
Name Origin:Named after the Swedish town, Ytterby.
Name: Thulium
Symbol: Tm
Atomic Weight: 168.93421
Atomic Number: 69
Element Classification: Rare Earth Elements
Discovered By: Per Theodor Cleve
Discovery Date: 1879 (Sweden)
Name Origin:Thule, ancient name of Scandinavia.
Name: Ytterbium
Symbol: Yb
Atomic Weight: 173.04
Atomic Number: 70
Element Classification: Rare Earth Elements
Discovered By: Jean de Marignac
Discovery Date: 1878 (Switzerland)
Name Origin:Named for the Swedish village of Ytterby.
Name: Lutetium
Symbol: Lu
Atomic Weight: 174.967
Atomic Number: 71
Element Classification: Rare Earth Elements
Discovered By: Georges Urbain
Discovery Date: 1907 (France)
Name Origin:Named for the ancient name of Paris, Lutecia.
Name: Lanthanum
Symbol: La
Atomic Weight: 138.9055
Atomic Number: 57
Element Classification: Rare Earth Elements
Discovered By: Carl Mosander
Discovery Date: 1839 (Sweden)
Name Origin:Greek: lanthanein (to be hidden).
Name: Cerium
Symbol: Ce
Atomic Weight: 140.115
Atomic Number: 58
Element Classification: Rare Earth Elements
Discovered By: W. von Hisinger, J. Berzelius, M. Klaproth
Discovery Date: 1803 (Sweden/Germany)
Name Origin:Named after the asteroid, Ceres, discovered two years before the element.
Name: Praseodymium
Symbol: Pr
Atomic Weight: 140.90765
Atomic Number: 59
Element Classification: Rare Earth Elements
Discovered By: C.F. Aver von Welsbach
Discovery Date: 1885 (Austria)
Name Origin:Greek: prasios and didymos (green twin), from its green salts.
Name: Neodymium
Symbol: Nd
Atomic Weight: 144.24
Atomic Number: 60
Element Classification: Rare Earth Elements
Discovered By: C.F. Aver von Welsbach
Discovery Date: 1925 (Austria)
Name Origin:Greek: neos and didymos (new twin).
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