Mendellev Cards

Mendeleev Cards

In this activity (second in a series), students create their own classification scheme of elements in a simulation of the process by which Dmitri Mendeleev organized information into a periodic table. They use cards on which elements are identified only by a letter, meant to disguise their identities.

Two options exist--teachers can focus student inquiry toward the standard grid-type form of the periodic table, or students can be encouraged to create their own classification structure. In both options, students are constantly challenged to defend the criteria they use for classifying elements into groups. In the historico-investigative method, students repeat historical experiments to determine the physical and chemical properties of the elements before classifying their properties. Mendeleev's classification used existing data and was a theoretical rather than investigative approach. His theory did however, lead him to predict the existence and properties of undiscovered elements. Their discovery provided empirical data to support his theory. A unique approach to a hands-on method of creating a Mendeleevian classification for "nuts and bolts" is proposed by Mark Volkmann in the January 1996 issue of The Science Teacher.

Option 1 -- Grid

Use the element cards sheets and the envelope form with student instructions and the rectangular grid on the back of the envelope form. Each student will need a set of cards and a scissors. Use the instructions below on a transparency, but only show one step at a time.

Separate the element cards using a scissors. Set aside the undiscovered element cards for later.
Arrange the elements into chemical families. That is, separate them into groups with similar properties. When you have them separated, explain to the instructor how you made your choices. Then share that information with your partners.
In one classification, the number of chemical families is between three and ten. If your classification does not fit this model, rearrange your cards so that you will have from 3-10 groups. When you have them separated, explain to your partners how you made your choices.
Now rearrange your cards into exactly seven families. When you have them separated, explain to your partners how you made your choices.
Arrange the elements in your families in vertical columns. When you have them separated, explain to your partners how you made your choices.
Now look for a pattern between families in the horizontal direction. You will need to use the undiscovered element cards where there is no element to fit the pattern. When you have them separated, explain to your partners how you made your choices. Decide on the best classification and use it to fill in the grid on the back of your envelope.
As a large group, the class must come to a decision as to which classification is the best.

Option 2 -- Student Shapes

Use the element cards sheets and the envelope form with student instructions, but do not use the rectangular grid on the back of the envelope form. Each student will need a set of cards and a scissors. Use the instructions below on a transparency, but only show one step at a time.

Separate the element cards using a scissors. Set aside the undiscovered element cards for later.
Arrange the elements into chemical families. That is, separate them into groups with similar properties. When you have them separated, explain to the instructor how you made your choices. Then share that information with your partners.
Now look for a pattern between families--use any shape you wish to show this connection between families. You will need to use the undiscovered element cards where there is no element to fit the pattern. When you have them separated, explain to your partners how you made your choices. Decide on the best classification. Get poster paper and glue or tape your classification system to it.
As a large group, the class must come to a decision as to which classification is the best.

Acknowledgements

Chemical and physical properties are listed in a format borrowed from the chemistry faculties at St. John's University and the College of St. Benedict, Collegeville, Minnesota.

Link to card file.

Link to next activity in the series.

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