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10 hours ago · Astatine is a chemical element; it has symbol At and atomic number 85. It is the rarest naturally occurring element in the Earth's crust, occurring only as the decay product of various heavier elements. All of astatine's isotopes are short-lived; the most stable is astatine-210, with a half-life of 8.1 hours. Consequently, a solid sample of the ...
10 hours ago · t. e. African Americans, also known as Black Americans or Afro-Americans, are an ethnic group consisting of Americans with partial or total ancestry from any of the Black racial groups of Africa. [3] [4] African Americans constitute the third largest racial or ethnic group in the U.S. after White Americans and Hispanic and Latino Americans. [5]
