Teacher Page
The Periodic Law
Materials
For 15 Groups:
Chemical
Barium nitrate
Calcium nitrate
Magnesium nitrate
Potassium chromate
Concentration
0.1 M
0.1 M
0.1 M
1M
Sodium carbonate
Strontium nitrate
Sulfuric acid
1M
0.1 M
1M
Distilled water
Lead shot
Silicon
Tin
Unknown salt solutions
Preparation
(26.1 g Ba(NO3)2/L)
(16.4 g Ca(NO3)2/L)
(14.8 g Mg(NO3)2/L)
(add 194 g K2CrO4 to 800 mL
water and dilute to 1 L)
(83 g Na2CO3/L)
(21.2 g Sr(NO3)2/L)
(pour 56 mL of conc H2SO4
into 900 mL water and dilute
to 1 L)
shot
(pieces with masses in range
of 10 g to 25 g)
(pieces with masses in range
of 10 g to 25 g)
(use the 0.1 M solutions of
Mg(NO3)2, Ca(NO3)2, Sr(NO3)2
and Ba(NO3)2 described above)
Equipment
For 15 groups:
2 safety goggles
1 50-mL graduated cylinder
1 spot plate
8 centigram balances
1 plastic wash bottle
2 dropper pipets
Amount
150 mL
150 mL
150 mL
200 mL
200mL
150 mL
200 mL
Sufficient
2 kg
15
15
Name
Class
Date
Lab – The Periodic Law
Introduction
When the elements are arranged in order of increasing atomic number, there is a periodic recurrence of
properties that leads to the grouping of elements in the periodic table. Elements in vertical columns form
groups or families that are characterized by marked similarities in physical and chemical properties.
These similarities are due, in a large part, to the fact that all the elements within a group have the same
outer-shell electron configuration. Even within a group, periodic trends in certain properties can be
observed. The properties of density and solubility of compounds, for example, are known to vary
regularly within groups of elements.
Objectives
1. To examine the periodic variation of the density and solubility of compounds within groups of
elements.
2. To determine the densities of certain elements in Group 14.
3. To determine the solubilities of certain salts of Group 2 elements.
4. To make predictions of densities of untested Group 14 elements and to predict the solubility of an
unknown Group 2 salt, based on the determinations made.
Materials
balance
1 reaction sheet
25-mL graduated cylinder
graph paper
distilled water
lead sample, Pb
silicon sample, Si
tin sample, Sn
0.10M barium nitrate, Ba(NO3)2
0.10M calcium nitrate, Ca(NO3)2
0.10M magnesium nitrate, Mg(NO3)2
1.00M potassium chromate, K2CrO4
1.00M sodium carbonate, Na2CO3
0.10M strontium nitrate, Sr(NO3)2
1.00M sulfuric acid, H2SO4
Unknown salt solution
Safety





Wear safety goggles.
A number of the chemicals used in this experiment are toxic and/or irritating to the skin. Avoid contact with these
chemicals and wash your hands thoroughly after use.
Sulfuric acid is corrosive and can cause severe injury. If you spill acid on yourself, immediately flush the affected
area with water for 2-3 minutes and notify the teacher. If acid should get into your eyes, begin flushing your eyes
with running water immediately and continue doing so for at least 20 minutes. If there is an eye wash fountain in
the laboratory, use it.
If acid is spilled on the laboratory bench or on the floor, neutralize the spill with solid sodium bicarbonate,
NaHCO3, before wiping it up with sponges or paper towels. The acid has been neutralized when bubbles of gas no
longer form after addition of the sodium bicarbonate. If you need to dispose of a small quantity of acid, neutralize
the sample with sodium bicarbonate before pouring it down the drain.
Wash your hands thoroughly after completing this experiment.
Procedure
PART A: Densities of Group 14 Elements
1. Record the appearance of each of these elements on your data table 1.
2. Find the mass of each solid metal sample (Sn, Pb, Si) and record each mass on data table 1 (be sure to include units
on all your data!)
3. Fill a 25-mL graduated cylinder approximately half full with water. Record this initial volume of water on your
data table (remember to estimate between the lines!)
4. Hold the graduated cylinder at an angle and VERY GENTLY place one of the solid metal samples in the graduated
cylinder with the water letting it slide down the side of the cylinder, being careful not to spill any of the water.
Record the new volume on your data table.
5. Calculate the volume of the metal and record this value on your data table.
6. Repeat steps 4-5 for the other two metal samples.
Mg2+ Ca2+ Ba2+
PART B: Solubilities of Salts of Group 2 Elements
7. Obtain a reaction sheet.
- Add 2 drops of Mg(NO3)2 solution to the sheet.
- Add 2 drops of Ca(NO3)2 solution to the sheet.
- Add 2 drops of Ba(NO3)2 solution to the sheet.
(7) H2SO4
(9) Na2CO3
CAUTION: Soluble salts of barium are extremely toxic.
Avoid contact with these chemicals and wash your hands thoroughly after
use.
8. Add 2 drops of 1M H2SO4 solution to the drops from step # 7 to provide sulfate
ions for reaction with the Group 2A metal ions.

If the metal sulfate salt (MgSO4, CaSO4, or BaSO4) is insoluble in water, a precipitate will be formed
upon addition of H2SO4.

Record the solubility of each metal sulfate salt as S (soluble) or I (insoluble) in Table 2.
CAUTION: At a concentration of 1M, H2SO4 is a contact irritant and should be used with care.
9. Repeat step 7 and 8, BUT replace the 1M H2SO4 in step 8 with 1M Na2CO3 adding 2 drops to each well.

Record the solubilities of these metal salts in Table 2. (S or I)
 Wipe your reaction sheet with a paper towel and throw the paper towel away. Rinse the sheet with water
and dry thoroughly.
Name _____________________________________Period ____________
Data
PART A:
Table 1: Densities of Group 14 Elements
Sn
Pb
Si
Appearance
Mass of metal
Volume of water alone
Volume of water + metal
Volume of metal
PART B:
Table 2: Solubilities of Salts of Group 2 Elements
SO42-
CO32-
Mg2+
Ca2+
Ba2+
Unknown #_____
Analysis
1. Calculate the densities of the Sn, Pb, and Si.
Sn =
Pb=
Remember: Density = mass (g) / volume (mL)
Si =
2. Prepare a graph of density versus period number for Sn, Pb, and Si. Place the period number on the x-axis
and the density on the y-axis. Draw a best-fit curve through your data points and (0,0).
3. What is the identity of your unknown salt in Part B?
Conclusions
1. Based on your graph, estimate the density of germanium. Compare your estimate with the accepted density of Ge
which is 5.46 g/cm3.
2. Calculate the percent error between your estimated value and the accepted value for the density of germanium.
Discuss possible sources of error.
accepted value – experimental value
percent error =
 100
accepted value
3. Examine the following values for the density of carbon:
C (diamond) = 3.52 g/cm3
C (graphite) = 2.6 g/cm3
C (amorphous) = 1.6 g/cm3
a. Are these numbers consistent with your graph? Explain.
b. Why are there three different densities for carbon?
4. Summarize any relationship that you can discern in Table 2 between the solubility of alkaline earth metal salts and
the position of the metals in the periodic table.
5. Describe how you were able to determine the identity of the alkaline earth metal ion in the unknown solution.