Properties of Representative Elements
Matt Grandbois, Eric Nelson, Sarah Madden, Darrin Fahrley
Chem 120H
9/12/00

Purpose:

    The purposes of this lab is to collect data in order to determine the properties of certain groups of elements.  To do this, we will test the elements’ metallic character, atomic size, electronegativity, ionization energy, and chemical reactivity based upon their location in the periodic table.

Procedure:

 There are five parts to this lab:

 Part 1  To seven different elements 5 milliliters of hot distilled water was added.  To those elements that did not react with the water, a few milliliters of HCL(aq) was added.  Data was recorded.  Trend was determined for reactivity based upon groups and periods.
 Part 2  A Magnesium ribbon is burned.  Ashes are collected.  Ashes are added to a 10 milliliter solution of distilled water and universal indicator.  Color is noted to determine pH.  The pH of various oxide solutions are tested.  Data is recorded and pH was determined.   A rule was determined based on observations.
 Part 3  The physical properties of the elements of group VA were recorded.  The data was used to arrange them in order of increasing metallic character.
 Part 4  A halide was reacted with a halogen.  The reaction was observed and the colors and layers were recorded.  The halogens were then ranked in order of reactivity.
 Part 5  The solubility of salts was tested. A solution of 0.1 M Na2CO3 was added to several solution containing representative metal ions.  The reactions were observed and recorded.  The solutions were then ranked in order of increasing solubility.  The procedure was then repeated with 0.1 M K2SO4.
   The procedure was repeated one more time with 0.1 M NaOH.

Data:
 

Questions:

 Part 1
 What happened to the valence electrons of those elements which reacted?  What do the results indicate about the relative reactivity of elements on the periodic table within a group and across a period?  The valence electrons of the elements that reacted were used in forming ionic bonds.  The elements Aluminum, Calcium, and Magnesium all gave up their valence electrons to form the ionic bonds, this is called oxidation.  The element Tin gained valence electrons in the reaction, this is called reduction.  The elements reactivity increases as you go down the groups and left across the periods.

 Part 2
 What do the elements whose oxides formed acidic solutions have in common?  Suggest a rule based on your observations.   The elements which formed acidic solutions were all non-metals. Since metal oxides are formed with ionic bonds, they form bases within aqueous solutions.   The rule we have determined is that metal oxides form ionic bonds, where as nonmetal oxides form covalent bonds.
 
 Part 3
 Which element is most metallic? Bismuth is most metallic
 Which element has the lowest density?  Nitrogen has the lowest density.
 Comment upon the trends for metallic character and density within a family based on your observations. We have observed that the higher a density an element has the greater the metallic characteristics it displays.

 Part 4
 Rank the halogens in order of increasing reactivity.  The least reactive halogen in liquid form was bromine, followed by  iodine, and the most reactive was chlorine.
 Write a balance net ionic equation for one reaction above.

Cl2(l) + 2NaBr(aq) ------> 2NaCl(aq) + 2Br-(aq)

 Part 5
 Is there any pattern which might relate solubility with location in the periodic table?

Conclusion:

 In this lab we learned many new things about the period table and reactions.  We learned that within a group on the periodic table, as you go down the group the density and metallic character increases.  We learned that as you go down the group of halogens, the elements become less reactive.  We learned that metal oxides within aqueous solutions form basic solutions because of the ionic bonds in which the metal oxides are bonded.  We also learned that if a substance does not react with water, it might react with an acidic solution.
 
 Lab Index