Wilbur 1. Baker
Jacksonville University Jacksonville, Florida
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Demonstrations of Simple Bonding Using ~ a ~ n e t ;
A l l types of simple bondmg can be demonstrated with iron washers, magnets, and steel balls. This is demonstration by analogy only and is not proof; however it is an inexpensive, effective, and legitimate teaching aid. Other workers have utilized similar methods for static and dynamic illustrations. Ramsey (1) used mercury, steel balls, and magnetic fields to demonstrate several atomic phenomena. Noller (3) made a model of the Walden inversion using magnets. Conway (5) floated bar magnets in water to show polyelectrolyte interaction. Wendlandt (4) attached ligands by magnets to central particles of complexes. Godfrey (5) uses magnets for the forces of coordinate bonds in his commercial model set. Morgan (6) placed magnets in large beads to show various aspects of polymerization. Lewis (7) used a pair of bar magnets in two orientations t o illustrate the possible directions of rotation of a pair of electrons in an orbit. Eichinger (8) has students use a pair of bar magnets to demonstrate for themselves the energy required to break a covalent bond. flat iron washers, Materials used here are poster board, glue, black paper circles cut by a '/&-in. paper punch, Alnico horseshoe magnets with a '/4-in. gap, and '/,-in. steel balls. Construction details and magnet orientations are shown in A, B, C, and D of the photograph; both sides of each construction are shown. To illustrate valence "shells" or s orbitals, glue clean single washers to poster board, draw a circle on the back, and trim neatly. To illustrate p orbitals, glue two washers '/a in. apart, draw a figureeight on the back, and trim. Electrons are indicated by '/,in. black circles. The reader can visualize the various combmations of washers, magnets, and steel balls shown in the 12 numbered segments of the photograph. (Objects are supported by corks to allow room for magnets beneath.) Structures 10 and 11 are surprisingly stable but 12 is not; one steel ball must be held by cellophane tape.
Lenered segments A, B, C, and
D show
A simple way to improve 12 would be to cut the central washer into six arcs. Students can be instructed to set these up and physically feel the interplay of forces or the change of force with distance. They can then go on to whatever more sophisticated concepts they are able t o comprehend. Other examples or materials can be used. Hybridization can be indicated by changing the shapes of the orbitals. Dipole forces and the other forces weaker than ordinary valence can be demonstrated by using less strong magnets. Short bar magnets, perhaps cemented on, might be useful. If metal-working facilities are available, three-dimensional shapes can be made of iron and magnetized. Types of Bonding Illustrated by Numbered Segments of Photograph
Ionic Covalent
1 2 and 3 4 (sigma bonding) 5 (coordination between ones and one w orbital) 6 (pi bonding) 7 (lone pair repulsion) 8 (rtntibonding) 9 (filled orbitals) 10, 11, and 12
Non-bonding Metdlic
Literature Cited (1) RAWEY,R. R., Phil. Mag., 23, 207 (1917). 24, 27i (1947). (2) Noller, C. R., J. CHEM.EDUC., B. E., J. CHEM.EDUC., 31, 477 (1954). (3) CONWAY, W. W., J. CHEM.EDUC., 34,223 (1957) (4) WENDLANDT, 15) GODFREY. J. C.. J. CHEM.EDUC.. 36. 140 (1959). (6j MORGAN,'^. w:, J. CHEX.EDUC:, 37, 206'(1960). (7) LEWIS,G. N., "Valence," 1st ed., Chemical Catalog Company, Inc., New York, 1923, p. 59 (ACS Monograph No. 14). (8) EICHINGER, J. W., "The Electron Chart," Charts, Rt. 4, Box 412, Tallahassee, Fla.. 1959, p. 32.
constrution details and magnet orientations.
Numbered segments 1-12 illurtrate types of bonding.
Volume 39, Number 3, March 1962
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