application/ and analogie~ UnderstandingElectron Configurations Davld F. Rleck Richard A. Henson School of Science and Technology Salisbury State Unlverslty Salisbury, MD 21801
Recently there have been proposed alternatives for diagrams to assist students in determining electron configurat i ~ n s l . Commonly, ~. a table is constructed in which the bottom row consists of subshell 1s. the second row consists of subshells 2s and 2p (the 2ssubshell being positioneddirectly above the 1s subshell). etc. T o ohtain electron configurations, students draw '&om diagonally from the bottom right to the top left (see figure). The argument against such a diagram is that students have difficulty aligning columns and drawing straight arrows. I t has been my experience that most students have more difficulty underitanding the purDose for determining electron configurations. I have successiully employed ananalogy that I recommend for use in secondary schools as well as in nonmajor sections of college general chemistry. Essentially, an electron configuration is used to determine "where" (i.e., what shell, subshell, etc.) electrons of an atom reside. By comparing an atom to an apartment building students are able to understand more quickly the concepts of subshells and orbitals. I draw parallels as follows: Shells correspond to floors of the building-the farther from the ground floor (n = I), the higher the energy. The subsbells correspond t o the apartments, and the number of apartments on any floor equals the floor number; i.e., the first floor of the building contains only one apartment (there is one subshell in the shell n = I), the second floor has two apartments, etc. The orbitals correspond to the rooms of the apartment, and all apartments have an odd number of I Grenda, S. C. J. Cham. Educ. 1988, 65,697. >Darsey,J. A. J. Chern. Educ. 1988, 65, 1036
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Journal of Chemical Education
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edited by: DELORENZO
Middle Georgia College Cachran, Georgia 31014
rooms; type s are one-roomapartments, type p are threeroom apartments, etc. Finally, only two people are allowed in any room, one male and one female (two electrons per orbital, one spin +1/2, one spin -112). A student can then equate a question pertaining to valence electrons to one pertaining t o the "people on the top floor of the building: how many neonle are there. where do thev live. and what are their sexes?" The analbgy can be extended incorporate Hund's rule; if three people get together to share a three-room apartment, each gets his or her own room. If a fourth person moves in, two people have t o share a room. While this is a simplistic approach to the meaning of quantum numbers and electron configuration (and certainly not an appropriate analogy for all students), nonchemistry majors have responded to it extremely well.
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Dlagrem used to determine elemon conflguratlon.
