AN ATOMIC MODEL CONTEST FOR MGH-SCHOOL STUDENTS
A method i s presented of increasing the interest of high-school chemistry students in the study of atomic structure and the periodic system. The essential features of this method are: (1)the organization of a contest; (2)the building of a static atomic model; (3) the preparation and presentation of a paper i n class describing the properties of the atom designed. The ideas for designing and building these atomic models came from the study of the subject mutter in the newer works of high-school chemistry. It can safely be said that a fundamental knowledge of the periodic system and atomic structure is of the greatest aid to the young student of chemistry, be he of collegiate or highschool age. But how are we to impress the high-school student, for example, with this f a c t ? Unless t h e teacher finds some stimulating method of presenting this knowledge and the principles involved therein, the study of the periodic system and atomic structure may hecome merely dull routine memory work. The writer of this article was faced with this problem in the beads at corners painted red. &hth cornk lower right foreground is painted with aluminum paint.
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After tly-
ina various methods. the suggestion for an atomic model contest was found in one of the newer works in high-school chemistry. The methods suggested for making atomic models were modified t o meet our particular needs.
Organizing the Contest The class consisted of twelve students. They were divided into six teams. Each team was to construct an atom or a molecule, and a t the same time prepare a paper or talk on the element represented by his particular 140
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model. The students thoroughly understood that the models were static and not designed to represent a dynamic atom. Prizes were offered to the winning team. In our case paper weights, a "Campanile" and "Golden Bear," were appropriate because of proximity to the University of California.
Instructions Each team was supplied with s a c i e n t annealed steel wire No. 8 B. & S. gage approximately one-eighth inch in diameter to make the sides of a single shell atom, the dimensions of which were a five-inch cube. For an atom such as chlorine (Figure I), the outside shell was a one-foot cube. Figure 2 represents a carbon dioxide molecule and a nitrogen atom. The corners were held by round wooden beads five-eighths inch in diameter. The laboratory vise held the beads, and the students used a one-eighthinch bit for drilling the holes. The beads were purchased from a toy shop and were of the type used for "Tinker Toys." An oval-shaped bead was used for the nucleus and the two electrons on either side of the nucleus were made by sawing an oval-shaped bead crosswise through the center. After the wire sides were made, and the holes drilled in the wooden beads, the model was set up by gluing the ends of the wires in the beads. The model was then painted. The helium nucleus was painted white and the number of excess protons was marked with ink. AU electrons were painted red, and the rest of the model was painted aluminum. We found that less than two hours' uninterrupted work by a team was necessary to construct a model, such as the lithium or beryllium atom. For such an atom, the cost of the wooden beads and the wire was approximately twenty-five cents.
Judging the Contest Judges were selected from the university. One member of each team gave a brief talk of from five to seven minutes on his model and on the physi-
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cal and chemical properties of the element which i t represented. Various references were used in the preparation of these talks. As an introduction a student gave a brief history of the periodic classification pointing out the periodic changes of the properties of the elements by means of a chart. An outline for a talk on the chlorine atom is given below: Name--Chlorine Symbal-C1 Melting point- -101.6"C. Boiling point- -34.6'C. Color of g a ~ g r e e n i s hyellow Atomic volume of solid ec.-23.52 Atomic weight-35.46 Isotope-35, 37 Atomic number-17 Electrons in various quantum levels: 1st-2 2nd-8 3rd-7
Heat of vaporization cal. per mole5000 Heat of fusion cal. per mole--1634 Solubility in water moles CIS per liter0.090 (1 atm.) Analytical Detection Estimation Granmetrically Volumetrically Interesting Reactions
Conclusion I n the judging of the contest two points were taken into consideration: first, the technic used in constructing the model; second, the knowledge of the subject matter shown by the student in his talk. References "Introductory Chemistry," New World Book Co., New York, 1927, 1. GORDON, pp. 363-5. HILDEBRAND, "Principles of Chemistry," Revised edition, The Macmillan Company, New York City, 1926, pp. 252-72. 3. LATIMERand H n D E B m . "A Reference Bwk of Inorganic Chemistry." The Macrnillan Company, New York City. 1929, p. 122. 4. LINCOLN, ''Physical Chemistry," D. C. Heath & Co., Boston, Mass., 1918, pp. 64-81. 2.
