Radioactive Rare Earth Elements
Actinide Series
Name: Neptunium
Symbol: Np
Atomic Weight: 237.048
Atomic Number: 93
Element Classification: Radioactive Rare Earth Elements
Discovered By: E.M. McMillan, P.H. Abelson
Discovery Date: 1940 (United States)
Name Origin:Named for the planet Neptune.
Name: Plutonium
Symbol: Pu
Atomic Weight: 244.0642
Atomic Number: 94
Element Classification: Radioactive Rare Earth Elements
Discovered By: G.T.Seaborg, J.W.Kennedy, E.M.McMillan, A.C.Wohl
Discovery Date: 1940 (United States)
Name Origin:Named for the planet Pluto.
Name: Americium
Symbol: Am
Atomic Weight: 243.0614
Atomic Number: 95
Element Classification: Radioactive Rare Earth Elements
Discovered By: G.T.Seaborg, R.A.James, L.O.Morgan, A.Ghiorso
Discovery Date: 1945 (United States)
Name Origin:Named for the American continent, by analogy with europium.
Name: Curium
Symbol: Cm
Atomic Weight: 247.0703
Atomic Number: 96
Element Classification: Radioactive Rare Earth Elements
Discovered By: G.T.Seaborg, R.A.James, A.Ghiorso
Discovery Date: 1944 (United States)
Name Origin:Named in honor of Pierre and Marie Curie.
Name: Berkelium
Symbol: Bk
Atomic Weight: 247.0703
Atomic Number: 97
Element Classification: Radioactive Rare Earth Elements
Discovered By: G.T.Seaborg, S.G.Tompson, A.Ghiorso
Discovery Date: 1949 (United States)
Name Origin:Named after Berkeley, California the city of its discovery.
Name: Californium
Symbol: Cf
Atomic Weight: 251.0796
Atomic Number: 98
Element Classification: Radioactive Rare Earth Elements
Discovered By: G.T.Seaborg, S.G.Tompson, A.Ghiorso, K.Street Jr.
Discovery Date: 1950 (United States)
Name Origin:Named after the state and University of California.
Name: Einsteinium
Symbol: Es
Atomic Weight: 252.083
Atomic Number: 99
Element Classification: Radioactive Rare Earth Elements
Discovered By: Argonne, Los Alamos, U of Calif
Discovery Date: 1952 (United States)
Name Origin:Named in honor of the scientist Albert Einstein.
Name: Fermium
Symbol: Fm
Atomic Weight: 257.0951
Atomic Number: 100
Element Classification: Radioactive Rare Earth Elements
Discovered By: Argonne, Los Alamos, U of Calif
Discovery Date: 1953 (United States)
Name Origin:Named in honor of the scientist Enrico Fermi.
Name: Mendelevium
Symbol: Md
Atomic Weight: 258.1
Atomic Number: 101
Element Classification: Radioactive Rare Earth Elements
Discovered By: G.T.Seaborg, S.G.Tompson, A.Ghiorso, K.Street Jr.
Discovery Date: 1955 (United States)
Name Origin:Named in honor of the scientist Dmitri Ivanovitch Mendeleyev, who devised the periodic table.
Name: Nobelium
Symbol: No
Atomic Weight: 259.1009
Atomic Number: 102
Element Classification: Radioactive Rare Earth Elements
Discovered By: Nobel Institute for Physics
Discovery Date: 1957 (Sweden)
Name Origin:Named in honor of Alfred Nobel, who invented dynamite and founded Nobel prize.
Name: Lawrencium
Symbol: Lr
Atomic Weight: 262.11
Atomic Number: 103
Element Classification: Radioactive Rare Earth Elements
Discovered By: A.Ghiorso, T.Sikkeland, A.E.Larsh, R.M.Latimer
Discovery Date: 1961 (United States)
Name Origin:Named in honor of Ernest O. Lawrence, inventor of the cyclotron.
Name: Actinium
Symbol: Ac
Atomic Weight: 227.0278
Atomic Number: 89
Element Classification: Radioactive Rare Earth Elements
Discovered By: Andre-Louis Debierne
Discovery Date: 1899 (France)
Name Origin:Greek: akis, aktinos (ray).
Name: Thorium
Symbol: Th
Atomic Weight: 232.0381
Atomic Number: 90
Element Classification: Radioactive Rare Earth Elements
Discovered By: Jons Jacob Berzelius
Discovery Date: 1828 (Sweden)
Name Origin:Named for Thor, Norse god of thunder.
Name: Protactinium
Symbol: Pa
Atomic Weight: 231.03588
Atomic Number: 91
Element Classification: Radioactive Rare Earth Elements
Discovered By: Fredrich Soddy, John Cranston, Otto Hahn, Lise Meitner
Discovery Date: 1917 (England/France)
Name Origin:Greek: proto and actinium (parent of actinium), it forms actinium when it radioactively decays.
Name: Uranium
Symbol: U
Atomic Weight: 238.0289
Atomic Number: 92
Element Classification: Radioactive Rare Earth Elements
Discovered By: Martin Klaproth
Discovery Date: 1789 (Germany)
Name Origin:Named for the planet Uranus.
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