Mendeleev's Periodic Table: It Was All in the Cards

The modern periodic table of elements, which is based on chemical properties and increasing number of protons, or atomic number, is different from the first periodic table developed by Dmitri Mendeleev in 1869. Mendeleev wrote the names, atomic weights, and physical and chemical properties of each element on a separate card, then arranged the cards to show trends or patterns. He discovered that the elements, when arranged in order of atomic number and by similar properties, formed a repeating periodic pattern. The patterns were so clear that Mendeleev predicted the locations on the table of undiscovered elements. In this activity you will simulate Mendeleev's technique of arranging cards into patterns.

Materials

Nine element cards

Scissors

Element Cards

Activity

1. Cut out the nine cards and shuffle them.
2. Pretend these are nine of the elements Mendeleev was attempting to arrange into a pattern.
3. Based on the information on the cards, place the cards so that they form a pattern that makes sense.

Follow-Up Questions

1. How did your group or arrange the cards?
2. Based on your arrangement, where would you put a card for an element that is a liquid with an atomic mass between 9 and 13? What would its atomic mass actually be?

Answers

1. Answers will vary, but most students will arrange the cards according to solids, liquids, or gases.
2. In the liquid category with an atomic mass of 11.

Extension

Look at the modern periodic table and find the elements that would not have fit correctly in Mendeleev's periodic table of increasing atomic mass. Explain why they do fit correctly in the modern periodic table.