Worksheet: History of the Periodic Table

In this worksheet, we will practice describing the history of the periodic table and the organization of elements by atomic number and other parameters.


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.


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

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