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Actinium is a chemical element; it has symbol Ac and atomic number 89. It was first isolated by Friedrich Oskar Giesel in 1902, who gave it the name emanium; the element got its name by being wrongly identified with a substance André-Louis Debierne found in 1899 and called actinium.
Marguerite Catherine Perey (19 October 1909 – 13 May 1975) was a French physicist and a student of Marie Curie.In 1939, Perey discovered the element francium by purifying samples of lanthanum that contained actinium.
In 1899, he discovered the radioactive element actinium, as a result of continuing the work with pitchblende that the Curies had initiated. After the death of Pierre Curie in 1906, Debierne helped Marie Curie carry on and worked with her in teaching and research. In 1911, he and Marie Curie prepared radium in metallic form in visible amounts ...
McKittrick Tar Pits – series of natural asphalt lakes situated in McKittrick near Bakersfield, California, US. The tar pits have trapped and preserved many Pleistocene Age animals. Pitch Lake – largest natural deposit of asphalt in the world, located at La Brea, Trinidad and Tobago. From this source many of the first asphalt roads of New ...
This is a complete List of National Historic Landmarks in California.The United States National Historic Landmark (NHL) program is operated under the auspices of the National Park Service, and recognizes structures, districts, objects, and similar resources nationwide according to a list of criteria of national significance. [1]
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In the late 1930s, the first four actinides (actinium, thorium, protactinium, and uranium) were known. They were believed to form a fourth series of transition metals, characterized by the filling of 6 d orbitals, in which thorium, protactinium, and uranium were respective homologs of hafnium, tantalum , and tungsten. [ 2 ]
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