The structure of the periodic table 

Therese Donatello                 Weber High School
                                  5252 W. Palmer St.
                                  Chicago IL 60639
                                  (773) 637-7500

Objectives:

The Jr. High student will be able to:
1. understand the structure of the atom,
2. relate the structure of the atom to the structure of the periodic table,
3. use the periodic table to form compounds.

Materials Needed:

Paper (various colors)            Compasses             plastic bags
Periodic tables                   Box                   balance
Styrofoam balls                   Marbles
Glue                              Toothpicks
Scissors                          Tissue paper

Strategy:

1. History of the structure of the atom. 
   Use a box with demensions of at least 30 cm x 10 cm x 10 cm.  Cut off the 
   front and back of the box leaving about 2 cm at the top of the box.  Cut
   two pieces of tissue paper the size of the front and back openings.
   Make cuts at 0.5 cm intervals from the bottom to 2 cm below the top of the
   paper.  Glue the tissue paper to the front and back openings on the box.
   Cut a 2 cm styrofoam ball in half and glue one half to the bottom of the box
   in the center.  
   Have the students line up and as they come up to the table with the box on 
   it, give them a marble and have them shoot it into the box.  Record on a
   chart the number of times the marble exits the box, stays in the box, or
   comes out the front of the box.
2. Constructing a model of the atom.
   Give each student a bag containing a compass and 0.5 cm circles of paper.
   The circles should be two of one color of paper and the rest of a  
   different color of paper.  Have the students draw a circle that will be as
   large as the paper and then make another circle 1 cm smaller.  Have the
   students place the two circles of the same color on the smaller circle and
   the rest on the larger circle.  These will represent the electrons.  Now
   ask the students to come up and get the number of 1 cm circles that they 
   need to represent the protons in their atom.  They should take the same
   number of 1 cm circles as they had 0.5 cm circles.  Have the students look
   at the periodic table and connect the number of protons to the same number
   on the table.  Then ask them to write the name of their element on their
   paper.
   Place twenty-five pennies minted before 1982 on one side of a balance
   and twenty-five pennies minted after 1982 on the other side of the 
   balance.  The balance will tip downward on the side with the pennies
   minted before 1982.  Ask the students what part of the atom this 
   illustrates.  They should respond that it is the neutron.  Since all the
   coins were pennies the fact that the pennies do not balance shows the 
   idea of isotopes.  [Pennies minted after 1982 contain zinc and copper and
   therefore are lighter than the pennies minted before 1982 which are 
   composed of only copper].
   Have the students look at the periodic table and find their element and
   notice the number that is not a whole number.  It is not a whole number
   because it is the average of all the isotopes of that atom.  Have the
   students round off the number to a whole number and then come up and
   get the number of 1 cm circles of a different color to represent the
   neutrons in their atom.
3. Using the Periodic Table.
   Make a model of an atom having one electron in its outer level and 
   another having seven electrons in its outer level.  Use a large styrofoam
   ball to represent the nucleus and attach smaller styrofoam balls around
   the large ball with toothpicks.  Ask the students,"Which would require less
   energy?  The gathering of seven electrons by the atom with one electron or
   the capturing of one electron by the atom with seven electrons to make the
   compliment of eight for stability."  They should see that it requires less
   energy to remove one electron than it does to remove seven electrons.

Performance Assessment:

1. The students will be given papers with the headings [Atomic number,element,
   atomic mass, number of protons, number of electrons, number of neutrons, and
   number of electrons in the 1st, 2nd, and 3rd level].  Place one piece of
   this information for each element and have the students fill in the rest of
   the information using their periodic tables.  [Do not use the number of
   electrons in the 1st, 2nd, or 3rd level as one of the pieces of information
   unless you give all three levels of electrons.  It would be better to give
   just the number of electrons to see if the student understands the 
   arrangement of the electrons on each level].
2. The students will be given paper models of atoms showing them to either need
   electrons [indentations in the circles] or giving electrons [projections 
   on the circles].  By connecting the proper circles a compound will be 
   formed.  After using the circles the student should be able to look at the
   periodic table and use it in place of the circles to form compounds.  The
   elements in the first two columns will give up their electrons while those
   in columns 16 and 17 will accept electrons thus forming compounds.