Lab 5.4 – Mendeleev
Cards
Purpose: To create your own classification scheme of elements in a simulation of the process by which Dmitri Mendeleev organized information into a periodic table.
Background:
Dmitri
Mendeleev is best
known for his work on the periodic table; arranging the 63 known elements into
a periodic table
which he published in Principles of Chemistry in 1869. Dmitri
Mendeleev was born at Tobolsk,
Siberia in 1834 and died in 1907. He studied science at St. Petersburg and
graduated in 1856. In 1863 he was appointed to a professorship and in 1866 he
succeeded to the Chair in the University. 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. This organization surpassed attempts at classification by Beguyer de Chancourtois and Newlands and was published a year before the work of Lothar Meyer. Visit the link below for a
more involved history of the development of the periodic table.
http://www.oocities.org/perry_science/acadchem/ch5/periodictablehistory.html
Classification and re-classification of objects can
have great value and purpose. Consider
the story below.
The Fable of the Lost Child
Like all good chemistry stories, this one begins ... Once upon a time, a child was visiting a landfill with his family. They were searching for used materials to recycle. Somehow, in filling their van with trash, they overlooked the fact that they had left one child behind. When the child discovered he was alone, and that night was approaching, he realized he would need a fire to keep warm. So he went in search of fuel for a fire. He gathered these materials (marbles, tree limbs, broom handles, flagpoles, paperweights, rocks, pencils and chair legs) and discovered that some things would burn, and others would not. To avoid collecting things that wouldn't burn, the child made a list. This list was very helpful, but soon, flagpoles and tree limbs and broom handles became scarce. The child looked for a pattern in the list that might lead him to new fuels. The next day the child went looking without his list, but he remembered his conclusion. He used it to bring back materials based on his conclusion -- successful predictions -- and avoided others. The child became confident of his conclusions (and wondered where his parents were!), and returned to the fire with three pieces of pipe, two pop bottles, and the axle from an old car. He did not bring back a huge box of newspapers. During the long, cold night that followed, the child devised another conclusion.
1. From the initial materials that the child gathered, what would his list look like?
things that burn:
things that don’t burn:
2. Based on the things that the child collected the second day, what conclusion might he have drawn from his list?
3. What might the child have done during the “long cold night” that might would help him revise his conclusion?
Procedure:
1. Separate the element cards (page 1 and page 2) using a scissors. Set aside the undiscovered element cards for later.
2. Put the elements in order from lowest to highest element mass.
3. Arrange the elements into chemical families. That is, separate them into groups with similar properties. For example, you might put all elements with melting points above 0oC in one group and those below 0oC in another. Or you might group the elements by the number of chlorine atoms (Cl) in a chloride compound.
4. Examine the elements within each chemical family for any patterns. Arrange the elements in each family in some logical sequence.
5. Now look for a pattern between families. Make a chart using 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 are satisfied with your chart, tape it onto a sheet or sheets of paper.
Conclusions & Extensions:
1. Describe the process by which you organized your element chart.
2. Compare your element chart to that of another
student. How are they alike and
different?
Use the different styles of periodic tables here to help answer
question #3:
http://chemlab.pc.maricopa.edu/periodic/styles.html
3. By comparing the “Element Mass” to the atomic mass on the periodic table in your textbook (round off to the nearest whole number), you can identify which elements are on your cards. Write the real chemical symbol on each card.
a) How does your chart compare to Mendeleev’s table?
b) How does your chart compare to modern periodic table?
4. What are possible identities for the undiscovered elements? Explain your answers.
5. Why is it useful for scientists to organize elements in a periodic table?