PITTSBURG STATE UNIVERSITY SCIENCE EDUCATION CENTER

Elementary Science Activity Number 8

Atoms and the Periodic Table Wall Chart

Main Concepts: To familiarize the student with the basics parts of an atom and to begin to build an understanding of molecules, chemicals and the periodic table.

Background: The Bohr picture of the atom is one of the simplest to visualize. It invokes a central nucleus made up of protons (which carry a positive charge) and neutrons (which carry no charge). The nucleus is surrounded by electrons (which carry a negative charge) in different shells (sometimes called orbitals in deference to their similarity to planetary orbits). Normal atoms have no net charge, and this means that they will have the same number of protons (postive charges) as electrons (negative charges). However, depending upon their electron structure, sometimes electrons are lost or gained by an atom, in which case, we have what is called an ion (same basic structure, but now there is either an electron or two missing, or an electron or two gained, therefore there is a net charge on an ion). Never-the-less, it is the configuration of the electrons (particularly those in the outer shells, most distant from the nucleus) which generally define the chemistry of an atom. The periodic table was constructed to help keep track of just these properties. Each column of the table contains elements which have similar outer electron configurations and therefore similar chemistry. Each row of the table tells you how many electron shells an atom has.

Materials:

Procedure:

Ask each student to pick an element (best start small).
Have them each draw a picture of the atom using the Bohr model. color the protons in the nucleus once color and put a positive sign on each. Color the neutrons in the nucleus a second color. Draw in the electron shells. With the exception of the valence electrons (those which will be shared or lost during chemical bonding), draw in the electrons and color them a third color and place a minus sign in each. Cut out as many circles of paper (the size of the electrons) as needed for the valence electrons and color these the same as the other electrons (again placing a minus sign in them). Put a bit of weak double stick tape (or folded tape) on the back of the electron (it will need to come off and on the diagram), and then attach these in their proper orbits.
In the upper left-hand corner place the atomic number (the total number of protons in the nucleus) of the element. In the upper right-hand corner place the atomic mass (you can use the number of protons plus the number of neutrons in the nucleus as a good approximation of this mass). Centered across the bottom write in the name of the element and centered below that the symbol for the elements. This element is now ready to be hung on the wall and might look something like this:
On a much smaller piece of paper (say 10 cm by 12 cm) put the chemical symbol in large font in the center of the paper, the element name centered across the bottom, and, again, the atomic number in the upper left-hand corner, with the atomic mass occupying the upper right-hand corner.

This will allow you to build another periodic table to lay on a table top. As you build this table you can ask your students to bring in materials (or find them in the classroom) which are made from each element, for example, water would go either on hydrogen or oxygen, glass on silicon or oxygen, etc. (Some elements will, however, be very hard, if not impossible to find examples of).
Molecular bonding can be shown by taking down two elements (such as Na and Cl) and removing the valence electron from the Sodium (Na) atom and placing it on the Chlorine (Cl) atom. Now the Na ion has a net positive charge or +1, and the Cl ion has a net electric charge of -1, so there is an electrostatic force which holds the two together. This illustrates an ionic bond. For something like water, the two hydrogen atoms share their electron with the oxygen atom which, in turn, shares one of its electrons with each of the hydrogen atoms. For this type of bonding (covalent bonding) the electrons which are shared should be moved to the edge of the page of each atom.
The difference isotopes) of each element can be added to the table very easily by drawing the additional isotopes on separate pages and tacking them up behind the main isotope.

You can soon build up your periodic table (although the electron shells will quickly become rather ungainly) which can be used to illustrate molecules and atomic bonding. You might want to make sure that each student prints their name at the bottom of each element's page so that when parents come to visit, they can look for their one child's contribution to the periodic table.

A Bit More for the Teachers

By putting together the table which allows you to remove elements for bonding, have several isotopes tacked up one behind the other, you will have at your disposal a very effecient tool for explaining much about atoms and chemistry. You can go a bit further by adding little symbols for atoms typically found as metals, gasses, noble elements, radioactive isotopes, etc.. On top of this, the students will get to have some fun drawing the atoms and get in a little practice with arithmetic by figuring out the number of neutrons which are in a particular isotope from the atomic mass and atomic number associated with the isotope. The table-top periodic table will allow the students to realize how the chemical elements impact their everyday life.

Probably the trickiest part of this whole procedure is getting the information on the elements (such as electron configuration, isotopes, etc.), however, you can get this information pretty easily from the Pittsburg State University Science Education Web Page. It is located at www.pittstate.edu/services/scied. Follow the chemistry links until you find a picture of a periodic table. If you click on that, you can find all you ever wanted to know about any of the elements. Give it a try!