Return to Chemistry IndexThe structure of the periodic table

Therese Donatello Weber High School

5252 W. Palmer St.

Chicago IL 60639

(773) 637-7500Objectives:

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 paperStrategy:

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.