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 |
| C 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 |
| K 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 |