Name: ___________________________________ Date: ___________________ Period: ______

Periodic Trends of Alkali and Alkaline Earth MetalsPurpose: To show that elements in the same group on the periodic table show similar

trends in solubility and reactivity.

Part 1: Solubility

In this part of the experiment, you will compare the solubility of compounds made from alkali metals to compounds made from alkaline earth metals.

Materials: Four large test tubes

Test tube rack

150ml of distilled water

Sodium Carbonate (Na2CO3)

Potassium Carbonate (K2CO3)

Calcium Carbonate (CaCO3)

Magnesium Carbonate (MgCO3)

Procedure:

1. Place about 1 gram (size of a pea) of each of the four compounds into separate test tubes.

2. Fill the test tubes about ¾ full with distilled water and stir with a stirring rod.3. Rinse the stirring rod with distilled water.4. Stir each solution very well for several minutes.5. Observe the test tubes and answer the following question.

a. Which 2 compounds are made from alkali metals? ___________________________________________________________

b. Which 2 compounds are made from alkaline earth metals? ___________________________________________________________

c. Define the word soluble: __________________________________________________________________________________________________

d. Which compound is most soluble?________________________________e. Which compound is least soluble? _______________________________f. In general, which are more soluble, compounds made from alkali metals

or alkaline earth metals? _______________________________________

Clean Up: All used contents of the test tubes may be rinsed down the sink with water. Clean all test tubes and laboratory material thoroughly to prevent cross contamination of chemicals.

Name: ___________________________________ Date: ___________________ Period: ______

Part 2: Periodic Trends in Alkaline Earth Metals

In this part of the experiment you will observe trends in reactivity of the alkaline earth metals. In this case, reactivity will be seen in the metal’s ability to form a precipitate in a reaction. More reactive metals are more likely to produce more precipitate.

Materials: Magnesium Nitrate Solution: Mg(NO3)2

Strontium Nitrate Solution: Sr(NO3)2

Barium Nitrate Solution: Ba(NO3)2

Calcium Nitrate solution: Ca(NO3)2

Potassium Chromate Solution: KCrO4

Ammonium Sulfate Solution: (NH4)2CO3

Ammonia Solution: NH4

Ammonium Carbonate Solution: (NH4)2CO3

Well Plate

8 Droppers

Procedure:

1. _____ Place about ½ a dropper full of magnesium nitrate into each of 4 wells in the same row of the well plate.

2. _____ Repeat step 1 with calcium nitrate in the next row of 4 wells.3. _____ Repeat step 1 with strontium nitrate in the next row of 4 wells.4. _____ Repeat step 1 with barium nitrate in the next row of 4 wells.5. _____ Add about ½ a dropper full of potassium chromate solution to the first well

only of the magnesium nitrate row.6. _____ Repeat step 5 for the remaining three rows. Make sure you add the

solution only to the first well of each row.7. _____ Add about ½ a dropper full of ammonium sulfate solution to the second

well only of the magnesium nitrate row.8. _____ Repeat step 7 for the remaining three row. Make sure you add the solution

only to the second well of each row.9. _____ Add about ½ a dropper full of ammonia solution to the third well only of the

magnesium nitrate row.10._____ Repeat step 9 for the remaining three rows. Make sure you add the

solution only to the third well of each row.11._____ Add about ½ a dropper full of ammonium carbonate solution to the fourth

well only of the magnesium nitrate row.12._____ Repeat step 11 for the remaining three rows. Make sure you add the

solution to the fourth well of each row.13._____ Observe and record your observations in the table below.

Name: ___________________________________ Date: ___________________ Period: ______

Data: Record your visual observations below.

KCrO4 (NH4)2SO4 NH3 (NH4)2CO3

Mg(NO3)2

Ca(NO3)2

Sr(NO3)2

Ba(NO3)2

Note: After all of the test solutions have been added, observe the patterns in the way that precipitates have formed. You should see that one of the alkaline earth metals always produces a lot of precipitate, and one that usually produces only a little.

Clean Up: Barium and chromate cannot be rinsed down the sink. Pour the used solutions in the well plate into the beaker provided. Use a wash bottle to rinse it into the beaker. Clean the rest of the well plate down the drain and wash the remaining equipment with water.

Name: ___________________________________ Date: ___________________ Period: ______

Questions: Answer the following questions. Your answers should be based on your

observations from part 2.

1. Which alkaline earth metal produced the most precipitate almost every time?

________________________________________________________________

2. Which alkaline earth metal produced the least precipitate almost every time?

________________________________________________________________

3. Rank all four alkaline earth metals, from least to most, in amount of precipitate

formed:

a. ___________________________

b. ___________________________

c. ___________________________

d. ___________________________

4. Compare your ranking in question 3 to the order that the alkaline earth metals

appear in the periodic table, what do you notice? _________________________

________________________________________________________________

________________________________________________________________

________________________________________________________________

5. In general, as you read down the column of the periodic table, are alkaline earth

metals more or less reactive? Why? ___________________________________

________________________________________________________________

________________________________________________________________

________________________________________________________________

6. How does this activity demonstrate that elements in the same group (column) in

the periodic table have similar properties? (Hint: What physical property was

observe in part 1 and what chemical property was observed in part 2?)

________________________________________________________________

________________________________________________________________

________________________________________________________________

________________________________________________________________