NOVEMBER, 1951
0
VALENCE AND FORMULAS TAUGHT WITH PLAYING CARDS FABIAN LIONETTI Boston University School of Medicine, Massachusetts
Tm
Boston,
use of devices as teaching aids in chemistry has long expedited the laborious task of making lucid the abstract or more intangible concepts. The utilization of models, figures, illustrations, and slides has become a necessary adjunct to the successful pedagogue's itinerary. Cards on which the chemical symbols were written proved valuable to such investigators as Newlands, Meyer, and Mendeleev who sorted the elements and catalogued their similarities. Recently, playing cards have been used to good advantage in teaching interrelationships of the periodic system.' The use of blackboard-size drawings of atoms and molecules has proved time saving, stimulating, and effective, especially in the secondary schools and in the Armed Forces training groups. As a result of an endeavor to simplify the teaching of valence and other features of combining capacity to students of undergraduate organic chemistry, the playing card concept was used to good advantage by marking the cards with the chemical symbols (one ele- ment per card) surrounding which the correct number -. MAXWELL, J. A,, J. CHEM.EDUC.,27, 510 (1950). of valences were represented as dash marks. These
JOURNAL OF CHEMICAL EDUCATION
600
were made up according t o the ratios of statistical occur- plies a group of carbons functioning as a stable unit and rence of the most abundant elements in organic com- double bond character of a different type than in acyclic combinations. I t is evident that groups of atmomsor pounds (i.e., C, H, 0,N, S, and P). The game of "Valence" is played using a deck of 50 radicals such as nitro, methyl, and amino might be into 100 cards which is dealt in hands to the participating troduced in place of the individual elements to reduce students. These hands are then played by building the number of cards to a smaller but equally workable number. Figures 2, 3, 4, and 5 show a few of the posmolecules according to the sible combinations. To synthesize a molecule, cards simple rules of combining are placed so as to attach the elements by means of the capacities,whichareinmany dash marks, using up the full quota of dashes on each cases simpler to remember card. Hence, the idea of constructing configurations than the playing rules of with correct valences is readily presented. Figure 3 canasta, pinochle, or bridge. illustrates the manner of synthesizing graphically an As a game the ~ r o i e c t be- . comes in many instances sig- n n n aldehyde (acetaldehyde) from which the corresponding acid (acetic) is derived by the simple insertion of an nificantly more rewarding, oxygen. Figure 4 demonstrates the use of the benzene informative, and even amusring in formulating benzene and nitrobenzene; the ine to the student as commanner of building hydrocarbon chains with unsatura1 pared to the rigors of con- 1 tions is presented in Figure 5. With students lacking a ventional methods of teachF~ a knowledge of chemistry it was observed they readily ing such concepts. Figure 1 illustrates the manner of marking the cards. It will be acquired the ability to make appropriate "workable" noted that several "kinds" of carbon, oxygen, and nitro- combinations of elements into carbon chains with the gen are included, showing distinctions betweensingle and functional groups properly appended. They were double bonded elements aswellas properlyrestricting the agreeably surprised in many instances after winning a manner of using some of these according to the known hand to find they had synthesized a substance with rules of chemical combination. Tetravalent and double known chemical and physical properties and with which they were already familiar (such as the acid of vinegar and alcohols of grain or wood). To aid and stimulate interest in chemistry, large placards were made up on which common functional groups were drawn as headings to columns and the properties of each type as well as examples and uses were tabulated in the columns. Using these as models, students are able t o channel their card-matching efforts toward the construction of common, well-known formulas. For chemists, colleagues, and associates who are well grounded in fundamentals of chemistry and who might have tended to look upon the playing card concepts of valence with some levity and facetiousness, a game was devised, similarly called "Valence," which has since become a favorite pastime at lunch, during train travel enroute from meetings, or at smokers and the like. This game is played by dealing seven cards t o each of the participants, and follows the general principles of conquian or rummy as played with conventional playing cards. The balance of the deck is placed in the center of the table and cards are drawn and discarded in sequence by the players until a player "builds" amolecule. When a player has the proper cards with connected valence markings to lay down a molecule, he calls for a showdown (in his turn). In this particular game the scoring is done by adding the atomic weights of the atoms in the compound synthesized. The player calling the showdown may or may not have excess cards in his hands. If he does, he may win the hand only by possessing a sum of weights of unmatched cards less than that of the unmatched cards held by any other player. bonded carbon, the methyl and methylene groups, and For instance, Player A may call for a showdown at his individual elements exhibiting variable valence are turn to draw a card from the pack, having synthesized shown. The benzene nucleus shown on one card im- acetaldehyde, CHBCHO,and having one carbon and one
-
u
NOVEMBER, 1951
601
hydrogen left over. The sum of weights of the unmatched cards in this case is 12 (C) plus 1 (H) equaling 13. If no other player, at the time of the showdown, is able to put down unmatched cards totaling less than 13, Player A wins the hand with a score equal to the molecular weight of the compound he has made. Simultaneously, deductions are made from the scores of the other players equal to the sums of cards they cannot
- . f3+6Rc c H
t
4
\
H-F c$-H u-c -H
'C'
:,
Figure 4
bons) bonus. The other alternative is not to hold this card and avoid the risk of a 72-point deduction in case of a loss. Another instructive and enjoyable pastime has been the playing of the cards similar to the game of dominoes. In this, the cards are divided among the participmts and are played in sequence, face up and one at a time. The group works towards synthesizing one molecule in the center of the hoard hut the winner of each game is the first player to complete any known formula. The molecular weight of this substance may he credited to a point score if desired. When one considers the infinite number of games possible by matching the cards in the conventional type of deck, it is at once obvious that numerous analogous games may be improvised using chemical playing cards. Many such variations have been tried, but complete and workable rules for most are still being evolved. Practically each time a hand is played an enterprising player has some suggestion to make which enhances the instructive, or amusement, value of the particular trial of the moment. In this regard many such constructively critical comments have served to put the present system on a facile basis. The cards, used instructionally, can definitely aid students as low as high-school level t o grasp quickly the concepts of combining capacity, formulas, molecular weights, and the manner of writing graphical formulas; whereas to the chemist the cards are a source of diversion and entertainment.
build into a simple h o r n formula. Smce it is nearly always possible to form combinations leading to H-O-H, N&, CS2,CHI, C02,and other simple molecules, many interesting possibilities result. Several game rules have evolved, such as: (a) the winning hand is that which contains the molecule with the highest molecular weight; (b) the player has an option to pick cards without discarding if he wishes to risk building a chain of atoms which requires more atoms than he is holding; (c) required combinations of atoms must conform to the rules of chemical combination (two hydroxyls normally do not coexist on a carbon, ketones are more stable than enols, and so forth); (d) molecules such as COz, CSn, HzO, and HnS are restricted to the use of the appropriately marked type of oxygen or sulfur; and (e) players are prohibited from picking up more than one card a t a time (from the top of discards or the top of the deck). In order to introduce the possibility of greater return for greater risk, two cards were made up containing the benzene nucleus (Ce). The holder of such a card has the option of holding it and drawing six hydrogens to make benzene, or drawing some such acceptable number ACKNOWLEDGMENT of cards to make combmations such as phenol, cresol, The author is indebted with thanks to Mr. Thomas benzoic acid, aniline, and so forth. If successful, this Courtney Lee of the School of Medicine fur preparing card represents a 72 (the sum of the weights of six car- the illustrations.
