applications and analogies
edited by RON DELORENZO Middle Georgia College Cochran, Georgia31014
Students were asked t11imafine that they were applying for:^ tmly'.odd"jolat thequantum ShoeStore. They would he hired only ifthry could prove hey understood the store's very unusual system of organization. They would have to learn to place shoes in the correct boxes on the correct shelves. When they went by to answer the employment add, the zany manager kept calling the store a n "atom". To him, a air of shoes were alwavs "two electrons". He called the shelves "enerh? levels", :md the students were asked ifthey would mind stavine late to dust "suhlevels". An entire area of the wacky stbrekad slanting shelves, and the manager insisted that they be kept that way. The model I built for the shoe store is shown in Figure 1. "Shelves" were made of bricks and boards. "Boxes" were plastic shoe boxes. The "shoes" or "pairs of shoes" were key tags marked with one or two arrows. (Also, you can increases the fun for the students by asking them to bring their own real shoes to use.) Each shelf was labeled with
a n index card to show its level and sublevel. Magnetic stick-on strips were attached to the backs of key tags and index cards, and to the front of shoe boxes and shelves. Shelf 1had only one level (a), and thus one shoe box. Shelf 2 had two levels (s and p) and four shoe boxes. Shelf 3 had three levels (s, p, and d) and nine boxes. Students were given the rules for the filling the shoe boxes. Shoes had to be placed inorder, going from the lower to the higher shelves. Each box could hold only one or two shoes, and they had to be placed i n opposite directions. Each box on any one subshelf had to receive one shoe before any box could hold a pair. Students were given the "shoes" and asked to fill the boxes in the correct order. The shoe store analogy for the order of filling energy levels from lower to higher potential energy is carefully established. Obviously, the rules for this analogy and the order of filling do not apply a t the 4s and 3d sublevels, so it is necessary to remodel the "shoe store" a s shown in Figure 2. Shelves were raised on one side to put them on a slant, and the familiar diagonal rule of filling the orbitals was introduced. I used a n overhead transparency of the new model and reiterated the rules. The students were given a worksheet similar to Figure 2 and asked to write the electron configuration and orbital notation of the first twenty elements. Another challenge is to introduce quantum numbers into the game. The shelves, suhshelves, and boxes were easily relabeled with the proper numbers and letters. Four quantum numbers were assigned to everyshoe, and the students were then asked to locate the shoe. This model can be modified using a stepladder or overhead transparencies.
F g ~ r e1 . E ectron Snoe Store. Tn~smoael shows the snoe ooxes paceo on me correct eve. and sLolevers. The arrows represent tne shoes (electrons)anc the oroer ot f ng the snoe ooxes (oroltas, according to Hund's rule.
Figure 2. Modified Electron Shoe Store. This model shows thecorrect order of filling the sublevels and orbitals.
The Quantum Shoe Store and Electron Structure M. Bonneau Cortland Jr.-Sr. High School Valleyview Drive, Cortland New York 13045
The following analogy helped my high-school chemistry students learn and apply the rules for filling energy levels, sublevels, and orbitals. Students had a lot of fun.They learned more quickly and retained the knowledge better with these physically and mentally active classroom exerC S R S. . .. .I~
J
Volume 68 Number 10 October 1991
837
