The Mendeleev Lab of 1869

Adapted from Holt Chemistry: Visualizing Matter, 2000

Problem:

 Use your knowledge of the periodic table to determine the identity of each of the nine unknown elements in this activity.

q       The unknown elements are from the following groups in the periodic table.   Each group listed below contains at least one unknown.

1          2          11        13        14        17        18

q       None of the known elements serve as one of the nine unknown elements.

q       No radioactive elements are used during this experiment.  The relevant radioactive elements include Fr, Ra, At, and Rn.

q       You may not use your textbook or other reference materials.  You have been provided with enough information to determine each of the unknown elements.

Procedure: 

1.      Inspect the properties of the known elements.

2.      Arrange the cards of the known elements in a crude representation of the periodic table. 

3.      Once the known elements are in place, inspect the properties of the unknowns to see where their properties would best “fit” the trends of the elements of each group.

4.      In your data table, assign the proper element name to each of the unknowns.  Record the symbol for each of the “unknowns” in your data table.

Data Table:

Be sure to make your data table so that you have enough space for all your unknown elements.

Conclusion:

Summarize your group’s reasoning for assignment of each unknown.  Explain in a few sentences exactly how you predicted the identity of the unknowns.

Li 
Physical State                  solid
Density                             0.534 g/cm3
Hardness                          soft, claylike
Conductivity                      good
Solubility (H2O)                 reacts with water
Melting Point                    180oC
Color                                 silver
Cl2 
Physical State                  gas
Density                             0.00321 g/cm3
Hardness                          none
Conductivity                      very poor
Solubility (H2O)                 slight
Melting Point                    -101oC
Color                                 greenish yellow
Ag 
Physical State                  solid
Density                             10.50 g/cm3
Hardness                          somewhat soft
Conductivity                      excellent
Solubility (H2O)                 none
Melting Point                    961oC
Color                                 silver
He 
Physical State                  gas
Density                             0.00018 g/cm3
Hardness                          none
Conductivity                      very poor
Solubility (H2O)                 none
Melting Point                    -272oC
Color                                 colorless
Cu 
Physical State                  solid
Density                             8.96 g/cm3
Hardness                          somewhat soft
Conductivity                      excellent
Solubility (H2O)                 none
Melting Point                    1803oC
Color                                
Na 
Physical State                  solid
Density                             0.971 g/cm3
Hardness                          soft, claylike
Conductivity                      good
Solubility (H2O)                 reacts rapidly
Melting Point                    98oC
Color                                 silver

Physical State                  solid
Density                             2.10 g/cm3
Hardness                          soft, yet brittle
Conductivity                      good
Solubility (H2O)                 negligible
Melting Point                    3550oC
Color                                 black
Ca 
Physical State                  solid
Density                             1.57 g/cm3
Hardness                          medium
Conductivity                      good
Solubility (H2O)                 reacts
Melting Point                    845oC
Color                                 silvery white
Unknown #8 
Physical State                  solid
Density                             1.74 g/cm3
Hardness                          medium
Conductivity                      good
Solubility (H2O)                 reacts slowly
Melting Point                    651oC
Color                                 silvery white
Unknown #9 
Physical State                  solid
Density                             11.85 g/cm3
Hardness                          very soft
Conductivity                      medium
Solubility (H2O)                 none
Melting Point                    303oC
Color                                 silvery white
Be 
Physical State                  solid
Density                             1.85 g/cm3
Hardness                          brittle
Conductivity                      excellent
Solubility (H2O)                 none
Melting Point                    1287oC
Color                                 gray
Sn 
Physical State                  solid
Density                             7.31 g/cm3
Hardness                          somewhat soft
Conductivity                      good
Solubility (H2O)                 none
Melting Point                    232oC
Color                                 silver
Ne 
Physical State                  gas
Density                             0.00090 g/cm3
Hardness                          none
Conductivity                      very poor
Solubility (H2O)                 none
Melting Point                    -249oC
Color                                 colorless
Br2 
Physical State                  gas
Density                             3.12 g/cm3
Hardness                          none
Conductivity                      very poor
Solubility (H2O)                 negligible
Melting Point                    -7.2oC
Color                                 reddish brown

Physical State                  solid
Density                             0.86 g/cm3
Hardness                          soft, claylike
Conductivity                      good
Solubility (H2O)                 reacts rapidly
Melting Point                    63oC
Color                                 silver
Ba 
Physical State                  solid
Density                             3.6 g/cm3
Hardness                          soft
Conductivity                      good
Solubility (H2O)                 reacts strongly
Melting Point                    710oC
Color                                 silvery white
Xe 
Physical State                  gas
Density                             0.00585 g/cm3
Hardness                          none
Conductivity                      very poor
Solubility (H2O)                 none
Melting Point                    -119.9oC
Color                                 colorless
In 
Physical State                  solid
Density                             7.31 g/cm3
Hardness                          very soft
Conductivity                      medium
Solubility (H2O)                 none
Melting Point                    157oC
Color                                 silvery white
I2 
Physical State                  solid
Density                             4.93 g/cm3
Hardness                          soft
Conductivity                      very poor
Solubility (H2O)                 negligible
Melting Point                    113.5oC
Color                                 bluish-black
Pb 
Physical State                  solid
Density                             11.35 g/cm3
Hardness                          somewhat soft
Conductivity                      poor
Solubility (H2O)                 none
Melting Point                    327.5oC
Color                                 gray
Ar 
Physical State                  gas
Density                             0.00178 g/cm3
Hardness                          none
Conductivity                      very poor
Solubility (H2O)                 none
Melting Point                    -189.2oC
Color                                 colorless
Ga 
Physical State                  solid
Density                             5.904 g/cm3
Hardness                          soft
Conductivity                      medium
Solubility (H2O)                 none
Melting Point                    30oC
Color                                 silvery
Cs 
Physical State                  solid
Density                             1.87 g/cm3
Hardness                          soft
Conductivity                      good
Solubility (H2O)                 reacts violently
Melting Point                    29oC
Color                                 silvery white
Unknown #1 
Physical State                  solid
Density                             2.33 g/cm3
Hardness                          brittle
Conductivity                      intermediate
Solubility (H2O)                 none
Melting Point                    1410oC
Color                                 gray
Unknown #2 
Physical State                  gas
Density                             0.00170 g/cm3
Hardness                          none
Conductivity                      very poor
Solubility (H2O)                 slight
Melting Point                    -219.6oC
Color                                 pale yellow
Unknown #3 
Physical State                  solid
Density                             1.53 g/cm3
Hardness                          soft
Conductivity                      good
Solubility (H2O)                 reacts violently
Melting Point                    39oC
Color                                 silvery white
Unknown #4 
Physical State                  gas
Density                             0.00374 g/cm3
Hardness                          none
Conductivity                      very poor
Solubility (H2O)                 none
Melting Point                    -156.6oC
Color                                 colorless
Unknown #5 
Physical State                  solid
Density                             19.3 g/cm3
Hardness                          soft
Conductivity                      excellent
Solubility (H2O)                 none
Melting Point                    1064oC
Color                                 gold
Unknown #6 
Physical State                  solid
Density                             2.54 g/cm3
Hardness                          somewhat soft
Conductivity                      good
Solubility (H2O)                 reacts rapidly
Melting Point                    769oC
Color                                 silvery white
Unknown #7 
Physical State                  solid
Density                             5.32 g/cm3
Hardness                          fairly brittle
Conductivity                      fair to poor
Solubility (H2O)                 none
Melting Point                    937oC
Color                                 gray

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