infight/ Electron Dormitory: Analogue Charles Morreale Mt. Lebanon Senior High Schwl 155 Cochran Road Pinsburgh. PA 15228
Analogous reasoning is the drawing of conclusions about an unknown based on information about a similar known object. I t is the ability to make connections between two unlike commodities by recognizing that they share a common trait or exemplify a common principle. The "Electron Dormitory Analogue" presented here provides students an opportunity to make connections between energy conservative methods of filling a dormitory with people and the energy conservation quantum theory of how electrons fill the noace around the nucleus of an atom. The following four steps are present in any analogy. The examole s "Electron Dormitory Analogue!' . eiven e x ~ l a i nthe Step 1. List the significant characteristics of the known: A student dormitory with a cantilevered structure inspired by FrankLloyd Wright. (See diagram.) The dorm has different floors or levels, which are subdivided into suites. By having only one ground-level suite, the dormitory design minimizes the complaint that many people have concerning traffic and noise associated with the rround floor. The student suites are identified using a number followed by a letter. The number tells the location: first level, 1; second level, 2; and so on. The letter s, p, d, or f, designates the suite's layout. Suite "s" is one room and requires the least energy to be occupied. Suite "p" is three rooms. Suite "d" is five rooms. Suite "f'is seven rooms and requires the most energy t o be occupied. These different suite layouts are r e ~ e a t e dthrouahout the dorm. However, due to energy conservation requirements and the shape and size of thedormitory, only suite "s" is found on each level. If space permits, then the next largest suite follows (p, d, f) in sequence. The pattern is first level, one suite (1s); second level, two suites (2s and 2p); third level, three suites (3s,3p, and 3d); etc. The dorm is filled by following common sense laws of energy conservation. In order to conserve energy, students fill the form like a glass of water, starting a t the bottom (lowest energy to highest energy). Only two students may share a room. Because students would rather not share their rooms, each room in a suite will have one occupant before any rooms are shared. A suite must be filled before students are placed in the next highest energy suite. Step 2. Infer a relationship between the less familiar and the more familiar analogue: There is a similarity hetween the size of the dorm selected and the size of a selected element's atom. A parallel can he made by comparing the student to the electron of an atom. Step 3. Map the inferred relationship onto the less familiar: This can be done by testing, experimenting, or working through similar pathways. Use the electron dorm with selected elements to show the electron distribution and the correct quantum notation. Step 4. Articulate what has been found, clearly relating the unfamiliar to the familiar: The terms "atom"and "electron" can be substituted into the known analogy. Students represent electrons. A specific element's atom represents the dorm size. Floors or levels represent the principle quantum number, n. Suites represent the sublevel shapes (s, p, d, f). The roomsare analogous t o the orbits (x, y,z) or (1,2,3,4,5). ~
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DONNABOGNER Wichita State University Wich~ta,KS 67208
The filling of the dorm with students follows Hund's rule: before a second electron can be placed in a given orbital, all the orbitals of that suhlevel must contain a t least one electron. Based on this foundation, chemistry students can be shown how the periodic table is similar to the electron dormitory diagram turned upside down. Using the periodic table as an electron tally. system, the teacher can easily show . the "4s" jump. Since conservation of energy is a major concern, it would take less energy for two students to occupy the one room of the "4s" suite than the five rooms of the "3d" suite. Anomalies of electron configuration like chromium can be explained with the analogy that students prefer not to share a room unless necessary. Therefore, one student in the "4s" suite moves to the "3d" suite. This creates a situation with one student in each room of the "3d" and the "49" suites. -I t is important to note that the quantum theory is just that. a theorv. Electrons are constantly in motion repelling each other i h i l e trying t o be as close to the nucleus as the balance of attracting and opposing forces permits. The quantum theory is an attempt t o organize the known facts; similarly, the electron dorm is an attempt to make quantum notation more manageable for the beginner.
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Journal of Chemical Education
Ganaral References v. ~~~
Adapted from Williams,.I Tmchinglor the Tmo-SidedMind:Prenti-Hall: Anderson. R.0.Chemistry 1970. (June), 27.
ELECTRON DORMIT0RY:ANALOGUE
m2 = the mu nombcr of o r b i d s for (n)
MAX OFTWOELECTROW PERORBITAL 2n2 = the mu nombsr of c l c s t m for (n)
Oiagrarn d lhe eleclron dormltov,
1983.
