(Encyclopedia) actiniumactiniumăktĭnˈēəm [key] [Gr.,=like a ray], radioactive chemical element; symbol Ac; at. no. 89; mass number of most stable isotope 227; m.p. about 1,050℃; b.p. 3,200℃±300℃; sp…
(Encyclopedia) Perot, H. Ross (Henry Ross Perot), 1930–2019, American business executive and political leader, b. Texarkana, Tex., as Henry Ray Perot, grad. Annapolis, 1953. In 1957 he resigned his…
(Encyclopedia) periodic law, statement of a periodic recurrence of chemical and physical properties of the elements when the elements are arranged in order of increasing atomic number. Such an…
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In 2016, the Academy of Motion Picture Arts and Sciences failed for a second consecutive year to nominate any African-American actors in the major acting categories, prompting director Spike Lee…
acid rain: Rain contaminated with pollutants such as sulfur dioxide and nitrogen oxide. These gases come from fuels being burned at high temperatures and from car exhausts. When acid rain falls, it…
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Lincoln, Abraham (president of U.S.): Shot April 14, 1865, in Washington, DC, by John Wilkes Booth; died April 15.Seward, William H. (secretary of state): Escaped assassination (though injured)…
