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 1800s, 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.


In Mendeleev’s periodic table, he placed the element titanium in the same group as carbon and silicon. Why should titanium not be in the same group as carbon and silicon?

  • ATitanium does not fit the pattern of atomic masses.
  • BTitanium is a nonmetal.
  • CTitanium has different properties from carbon and silicon.
  • DTitanium has a higher melting point than carbon and silicon.
  • ETitanium has a different electronic configuration than carbon and silicon.


Which of the following does not describe a way in which Mendeleev contributed to the development of the periodic table?

  • AMendeleev left no gaps in his version of the periodic table.
  • BMendeleev arranged elements in order of atomic mass.
  • CMendeleev predicted the properties of elements.
  • DMendeleev arranged some elements in periods.
  • EMendeleev arranged some elements in groups.


Which of the following does not describe a difference between Mendeleev’s periodic table and the modern periodic table?

  • AAll the elements are in the correct place.
  • BNoble gases were not present.
  • CThere are fewer elements.
  • DThe elements are arranged in order of their atomic mass.
  • EThere are gaps in the periodic table.


How is the order of the modern periodic table different from the order suggested by Newlands and Mendeleev?

  • AThe modern periodic table is ordered using atomic mass, not atomic number.
  • BThe modern periodic table is ordered using electronic configurations.
  • CThe modern periodic table is ordered using atomic number and atomic mass combined.
  • DThe modern periodic table is ordered using the properties of the elements.
  • EThe modern periodic table is ordered using atomic number, not atomic mass.


Considering the picture that shows a version of Mendeleev’s periodic table, which of the following statements is not true?

  • AMendeleev’s table does not contain a block for the transition elements.
  • BMendeleev swapped the position of iodine and tellurium.
  • CMendeleev’s table has gaps.
  • DMendeleev’s table includes the noble gases.
  • EMendeleev’s table does not show the atomic number.


In Mendeleev’s versions of the periodic table, the element tellurium comes before the element iodine. Why might this decision of Mendeleev’s have been challenged at the time?

  • AIodine has a greater atomic mass.
  • BTellurium and iodine have similar properties.
  • CIodine atoms have 53 protons, but tellurium atoms only have 52.
  • DMendeleev did not want to leave any gaps in the table.
  • ETellurium has a greater atomic mass.


Which of the following statements explains why Mendeleev left gaps in his periodic table?

  • ALeaving gaps allowed Mendeleev to finish his version of the periodic table before Newlands.
  • BLeaving gaps allowed him to group elements of similar properties together.
  • CLeaving gaps made patterns in the elements easier to identify.
  • DLeaving gaps left room for undiscovered elements.
  • ELeaving gaps allowed him to separate metals and nonmetals.

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