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 large part, to the
fact that all the elements within a group have the same outer-shell electron configuration. Even within a periodic group
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.
In this experiment, you will investigate the periodic variation of density and solubility of compounds within
groups. Specifically, you will determine the densities of certain elements in Group 4A and the solubilities of certain salts
of Group 2A elements. You will use your results to make predictions of the densities of other Group 4A elements and
also to predict the solubility of an unknown Group 2A salt.
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 4A.
3. To determine the solubilities of certain salts of Group 2A elements.
4. To make predictions of densities of untested Group 4A elements and to predict the solubility of an unknown
Group 2A salt, based on the determinations made.
Materials
 Lead shot, Pb
 Silicon, Si
 Tin, Sn
0.1M magnesium nitrate,

Mg(NO3)2




0.1M calcium nitrate,
Ca(NO3)2
0.1M barium nitrate
Ba(NO3)2
0.25M sodium oxalate,
Na2C2O4
1M sulfuric acid, H2SO4
1M sodium carbonate,
Na2CO3
1M potassium chromate,

K2CrO4
 Unknown salt solution
 Distilled water

Equipment
 safety goggles
 triple beam balance
 Spot plate
 Graduated cylinders
Actual Density Values:
Lead: 11.342 g/cm3
Silicon: 2.328 g/cm3
Tin: 7.30 g/cm3
Procedure:
Part A. Densities of Group 4A Elements
1. Determine the densities of the tin (Sn), lead (Pb), and silicon (Si) samples by the water
displacement method. Record the data in the data table. Note the appearance of these
elements and record observations.
2. Calculate the density of each metal. Compare with the actual densities given on the lab
sheet. Repeat the lab measurements if there is more than 10% error.
1
Part B. Solubilities of Salts of Group 2A Elements
1. Use a clean spot plate. To the row across add 5 drops of Mg(NO3)2 solution to each well. To the second row add
5 drops of Ca(NO3)2 solution to each well. To the third row add 5 drops of Ba(NO3)2 solution to each row. To the
fourth row add 5 drops of Sr(NO3)2 solution to each row. Note that these volume measurements need only be
approximate as this procedure is qualitative. CAUTION: Soluble salt of barium is extremely toxic. Avoid
contact with this chemical and wash your hands thoroughly after use.
2. Add 5 drops of 1M H2SO4 solution to each column going downwards to provide sulfate ions for reaction with the
Group 2A metal ions. CAUTION: At a concentration of 1M, H2SO4 is a contact irritant and should be used with
care. If the metal sulfate salt (MgSO4, CaSO4, BaSO4or SrSO4) 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 your data
table.
3. (a) Repeat step 3 replacing the 1M H2SO4 with 1M Na2CO3.
4.
(b) Repeat step 3 replacing the 1M H2SO4 with 0.25M sodium oxalate, Na2C2O4. CAUTION: Sodium oxalate is
toxic. Avoid contact with this chemical and wash your hands thoroughly after use.
(c) Repeat step 4 replacing the 1M H2SO4 with 1M potassium chromate, K2CrO4. CAUTION: Chromates are
both toxic and irritating. Avoid contact with this chemical and wash your hands thoroughly after use.
Record the solubilities of these metal salts in your data table.
PRE-LAB ASSIGNMENT:
1. Read through the procedure. Make notes on parts that are confusing.
2. Create a data table for density. Leave room for calculations beneath the data table. Include extra rows in the table in
case measurements need to be repeated for accuracy.
3. Create an observations table for the metals.
4. Copy the data table for Part B (below) into the lab notebook. Expand the table to allow room in the table for
observations.
During Lab: Follow the procedure and collect data. Take note of errors that occur and trends that you notice in the data.
Afer Lab: Write the RERUN conclusion. Include error analysis as shown by your calculations of percent error. Refer to
handouts on conclusion paragraphs for guidance.
PART B: Solubilities of Salts of Group 2A Elements
SO42-
CO32-
C2O42-
CrO42-
2+
Mg
Mg(NO3)2
Ca2+
Ca(NO3)2
Ba2+
Ba(NO3)2
Sr2+
Sr(NO3)2
Unknown
Unknown #
Identity of cation of unknown
2