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Lab: Mendeleev For A Day
As more and more elements were
discovered during the 1800s,
chemists began to categorize them
according to similarities in
chemical and physical properties.
A Russian chemist, Dmitri
Mendeleev (1834 –1907) was
more successful than most. He
noticed that when the elements
were ordered by increasing
atomic mass, there was a repetition or periodic pattern, in their
properties. By arranging the elements in order of increasing
atomic mass into columns with similar properties, Mendeleev
organized the elements into the first periodic table in 1869. Part of the reason Mendeleev’s table was widely accepted
was that he predicted the existence and properties of undiscovered elements. Mendeleev left blank spaces in the table
where he thought the undiscovered elements should go. By noting trends in the properties of known elements, he was
able to predict the properties of the yet-to-be discovered elements scandium, gallium, and germanium.
Unknown
A (precipitate?)
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Based on your observations, group the numbers of the unknown solutions into 3 families
according to similarities in their chemical behavior. (Hint: Each family contains 3 members).
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Family 2: !
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Family 3: !
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Questions
1. Why was this investigation called “Mendeleev for a Day?”
2. State two ways Mendeleevʼs periodic table differs from our modern periodic table.
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3. Why did Mendeleev leave blank spaces on his periodic table?
4. In this investigation, why didnʼt all members of the same family show identical reactions?
5. Give an example of two reactions from the same family that was similar but not identical.
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Be specific, giving: ! i.) the unknown numbers
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ii.) the test solution letters
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iii.) the specific observation(s) you made that supports your answer.