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


During the early 1,800s, scientists attempted to understand the chemical elements by sorting them. Which property of the elements was used to order them?

  • AAtomic number
  • BMelting point
  • CRelative atomic mass
  • DReactivity
  • EDensity


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


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
  • BLaw
  • CHypothesis
  • DTheory
  • EObservation


The Periodic Table is an example of a model: it allows scientists to make predictions by highlighting patterns in the properties of elements. The discovery of new elements allowed scientists to fill gaps and correct mistakes in the original Periodic Table. Which of the following words best describes the model used to construct the original Periodic Table?

  • AUnscientific
  • BFlawed
  • CWrong
  • DIncomplete
  • ECorrect


Henry Moseley revised the periodic table of Dmitri Mendeleev, changing the order of some of the elements. Which change did Moseley make to the organizing principles of the periodic table?

  • ASorting the elements by atomic mass
  • BSorting the elements by color
  • CSorting the elements by atomic number
  • DSorting the elements by atomic radius
  • ESorting the elements by melting point


The Law of Octaves states that the properties of elements repeat in steps of 8 when the elements are arranged in order of atomic mass. Who first observed this periodic trend?

  • AHenry Moseley
  • BLothar Meyer
  • CErnest Rutherford
  • DJohn Newlands
  • EDmitri Mendeleev


When the elements are sorted by their atomic numbers, periodic patterns in their properties are observed. Why are these patterns useful to scientists?

  • AThey allow predictions to be made when data is not yet available.
  • BThey provide strong evidence that the model used to organize the data is correct.
  • CThey allow other values to be determined without experimental work.
  • DThey allow the errors of experimental measurements to be determined.
  • EThey provide strong evidence that the experimental measurements are correct.

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