• Russian “nesting dolls” (often known as matryoshka dolls) have a long history in Russia.
  • The set seen above is unusual in that it has over thirty-five layers.
  • Because of the uniqueness of the electron configurations, these elements fit into the two boxes in the larger periodic table.
  • The word comes from the Greek “lanthanein” meaning “to be hidden.” The actinides are all radioactive elements and only the first four have been found naturally on Earth.
  • All of the others have only been made in the laboratory.
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