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Worksheet: History of the Periodic Table


During the early 1800s, scientists attempted to understand the chemical elements by sorting them. Which property of the elements was used to order them?

  • ADensity
  • BAtomic number
  • CReactivity
  • DRelative atomic mass
  • EMelting point


Periodic tables have been around for a couple of hundred years, and some of them look very different from the one we have today. What is it about periodic tables that makes them periodic?

  • AThey have rows as well as columns.
  • BThey are tables of information that are periodically updated to reflect our current knowledge.
  • CThey organize elements based on their periods of radioactivity.
  • DThey group elements based on their behaviors, which repeat periodically from the lighter to the heavier elements.
  • EThey arrange elements in reference to their reactivity with iodine—they are per-iodic.


Mendeleev’s periodic table was used to predict the existence of many unknown elements. Which term best describes the role of the periodic table in these predictions?

  • AModel
  • BHypothesis
  • CObservation
  • DTheory
  • ELaw


Dmitri Mendeleev developed the first periodic table to allow for elements yet to be discovered. Why did he leave gaps where others did not?

  • AHe was forgetful and missed some of the elements.
  • BOthers knew about more elements than Mendeleev, so they were able to fill the gaps.
  • CHe thought that it was more important that the table looked attractive, so he left artistic spaces.
  • DHe grouped elements by their behavior and left a gap if no known element fit his model.
  • EHe made his original table unnecessarily large by including duplicates of certain elements.