Molecular Models from Arrow Shafts Large-scale, three-dimensional models of molecules and lattice structures are valuable lecture aids. Models are especially helpful when students first encounter such geometries as tetrahedral, trigonal hipyramidal, and octahedral in the Valence Shell Electron Pair Reoulsion theorv. Large ball-and-stick m d ~ c u h m r d r l s r a n he readily wnrtrurttd f n m plastir fmm spheres nnd nrnw shnfts. Any school u:th ghysiral cducatiun r l a s ~ e ruhcrr archery i- taught invarid,ly ncrumulatri dsmacrd arnwi. D~amrdrdarnw shafts can be put 11, r m d wr. (31 recsrlcd, os ronncrtlng rvdi in molecular mudrlr, since t h q d ~ e the r i d h u i n y advantages: (1) They are of appropriate diameter and length. (2) Because they are wooden, they can be easily cut to length with a fine-tooth Saw and sharpened an the ends with a pencil sharpener. (3) Most shafts are already painted in solid, bright colors. (4) They are free and, a t many institutions, readily available. Cut the shafts intodesired lengths (I use6-in. lengthsfor anoctahedron) andsharpen both ends witha pencil sharpener (preferably an electric one). Then, with a twisting motion, force the tips into 3-, 4-, or &in. diameter molded plastic foam spheres (Frey Scientific Company). Although such connections are reasonably secure, they can be permanently glued with carpenter's or all-purpose glue. To differentiate between different bonds, such as axial and equitorial bonds in a trigonal hipyramidal structure, shafts of different color can be used. The spheres can also be painted different colors, if preferred.
Wayne L. Felty The Pennsylvania State University-Wiikes-Barre
Campus
Wiikes-Earre, PA 18708
278
Journal of Chemical Education
