Lewis diagrams (Pavia, Donald L.) - Journal of Chemical Education

Lewis diagrams (Pavia, Donald L.) William P. Jensen, and Donald A. Tarr. J. Chem. Educ. , 1988, 65 (10), p A271. DOI: 10.1021/ed065pA271. Publication ...
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User's Guide gives students sufficient information "to enter data and plot a few graphs without confusing them with all of the other features of the program." Although neither the documentation nor the format of the program implies that this package is a tutorial on graphing or data analysis, two of the seven pages in this introductory section do describe the process used t o find the relationships between variables using this program. The documentation contains no index, but the table of contents sufficiently describes the location of all topics. Teachers of introductory chemistry courses in high school or college might use this program t o have students find linear relationships when they apply a discovery approach to the topic of ideal gas laws or when they illustrate graphical methods of determining the order of a reaction for kinetics experiments. Physics teachers may find more applications than chemistry teachers. In f a d , most of the sample data files included with the program are drawn from physics experiments. In addition, teachers who wish to illustrate the graph of a certain function can do so by either modifying data files prepared by the author or by creating their own data files with DATAMAKER, a BASIC program also present on the disk. Instructions for both methods are included in the Teacher's Guide section of the documentation. Graphical Analysis I11 is written in BASIC. Clearly the author welcomes any user who wishes to make desired changes in the program. The back of the disk contains a fully remarked version of the programs. The documentation contains "Program Design Notes," a table listing the symbols for variables, a memory map, and instructions simple enoughto enablethe mast inexperienced of programmers t o make avariety of modifications. For example, some teachers may object t o the occasional use of sounds as signals; such sounds may be removed from the program. However, by using easily modified BASIC code the author has not sacrificed execution speed. Typical data analysis and graphing on the screen requires 10-20 seconds. When a delay occurs, the screen displays a message describing the activity. Printing times depend on the printer used. In addition to supporting conventional Apple1Imagewriter configurations, the program supports dot matrix printers interfaced with the Grappler+(TM) or t h e PKASORI(TM) card. The program's author, former physics teacher David Vernier, clearly understands the level of complexity and program transparency required for an applications program of this nature to be useful to high school and early college level students and faculty. Furthermore, Vernier Software continues support of its software purchasers by distributing a newsletter t o science teachers in which updates of programs are offered usually a t no cost. When a major revision does occur, owners of the old version are offered the new program a t a greatly reduced price. For example, purchasers of Graphics Analysis I1 may obtain Graphical Analysis I11 by returning the original disk and remitting a nominal $10 charge. The program is not copy protected. A letter from the author that accompanies the software states that the purchaser may make as many copies of the program "as you wish for use within your school a t no extra

cost." This very fair policy and the reasonable cost of this well-designed and versatile applications program should make it one that any science faculty would be anxious t o purchase and use with students. Caroline H. Bowers Spring Valley High School Sparkleberry Lane Columbia. SC 29223

DonaldL Pavra, COMPress. P.0 Box 102. Wentworth. NH 03282 Hardware: IBM PC (or compatible) with color graphics adapter Components: 1 disk and User's Manual Level and Subject: General Chemistry Cost: 540

This software is designed t o help students determine Lewis structures of molecules and ions. All 48 molecules and ions included in the program obey the octet rule; that is, all nonhydrogen atoms have eight electrons in theexpected answer. In addition todeterminine the correct Lewis structure. students are h&ed to understand the forn,al charge a~signmentof each alum :n a pnrtirular structure. They are expected to find the currect arrangement of atoms within the structure as well as the most logicalcharge distribution. In cases where more than one answer fits the rules the student is t o deduce the best Lewisstructure. Help is provided, if requested, every step along the way to a correct solution. The program is intended for college general chemistry students and students in a first-year organic chemistry course. This software could he used as an introduction to Lewis structure concepts, since no background in Lewis structure determination is assumed. A modest background in drawing Lewis structures and in the use of an IBM compatible computer would he helpful. A background in atomic structure, covalent bonding, and electronegativity concepts is assumed. The documentation clearly explains the features provided in the program and indicates the types of commands that are used. In addition, help is included a t each step in the procedure and a student can go to any level auicklv with s i m ~ l kevstrokes. e , Installation proredurea needed L O run the program for the first timenresimply expinin~d. However,thispn~cedurcdidnot workdue to ~

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failure of my system t o recognize the B drive. I was not able to install DOS on the disk provided and was forced to begin the program each time using commands not included in the directions. Once the installation procedure is complete there is, according to the directions, no way to change the parameters. Required tables such as a periodic table, valence electron tahle, etc. are readily accessible from any point in the program, although a novice computer user would do well to have these tables available in hard copy. After the program is initially loaded disk I10 operations are performed quickly, and students are not required to wait for extended oeriods of time while internal tasks are completed. The program behaves as claimed in the documentation and no surprises were encountered in the execution of the software. Needed calculations may be done without aid of any kind and results can be printed out a t the end of a session with a minimum of difficulty. Students have a number of rules and manipulations to master and probably need to use the program several times to gain the maximum benefit. The first time through students will understand the rules and operations of the program. During all succeeding times students will learn to apply this information t o produce Lewis structures. Prompts are unambiguous and helpful and one may easily recover from almost any situation with a minimum knowledee of eompurer operations. When nn answer is tl, he submittrdforanalysirtheroftunreisat~letu handle errors in an mformat~veand helpful fashion. T h e programmer has cleverly adapted the program to recognize correct as well as different types of incorrect answers even when a variety of answer formats is possible. Atoms, bonds, and lone pairs may he placed in any orientation as long as the answer is correct. Many incorrect answers produce clues that help identify the problem, and the HELP command allows students to work their way out of a problem. If the students have no idea how to correct a problem, the answer is iust a keystroke away. The program may be used by individuals, small groups, or by an instructor in a large classroom setting. The atoms, bands, and electron pairs are displayed in characters sufficiently lmge to be displayed using a LCD screen overhead projector. Instructors may choose to generate any of the 48 structures available. Bonds and especially electron pairs that often are not seen on the chalkboard from the back of a large room are clearly visible in this display. (Continued on page A272) ~

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Number 10

October 1986

A271

REVIEWS The software cannot he easily listed or modified. From the instructions i t appears t o he copy protected, and must he installed before use. Thus only one individual or group a t a time may use the software. The use of color is well done and clearly adds to the value of the software. I t does, however, limit the use of the software to corpputers with color capability. The colors are last when projected by an LCD screen projector, and students who had used the program commented a n the difference. The chemistry presented is accurate. Within the restriction that all molecules must obey the octet rule, the structures tested are correct. Where more than one Lewis structure is possihle the user is told which choice is best, within the rules presented, and reminded that other "resonance" structures are possihle. LEWIS DIAGRAMS can he used as a tutorial program. An option available from the main menu allows a student t o choose the Lewis Diagram tutorial, or t h e Formal Charge tutorial. I t may also he used as a drill and practice program by having the student use the "select a problem" option. The reward for a correct answer is a new problem. The student may select other options hy a simple procedure. The objectives of the program may he accomplished hy a paper and pencil exercise, hut the interactive component of the program would he lost. In addition, the effective use of color and easily read menu choices of atoms, single, double, and triple honds, and electron pairs would also be missing. The use of the computer does not save time. I t requires additional time t o master the techniques of molecule construction, hond selection, electron pair addition, etc., hut many students would he willing t o spend the extra time t o avoid the frustration of not being told where their logic is flawed. A comment I heard over and over was "Once I gat through the tutorial and intu the prohlemr it wa\ kind of fun." Another comment was "the program is self explanatory". This comment came only after the student hecame familiar with the operation of the program. The software was tested on students a t the freshman level and on senior chemistry majors. Both groups reacted favorably t o the exercise. I suspect that graduate students would also benefit from the program as a review exercise. The program was tested with students using little instructional help other than that provided by the program. I t was also tested with the instructor looking over the student's shoulder. I t worked best when the instructor helped the students get started and then left them alone. Students made a number of mechanical errors running the program, hut once they mastered the computer operations they could work on their . ~ own. ~ . . One improvement that I would like t o w e incorporated is an optiun to page through correct answers without first having tu construct themuleculesonesrrpat a time. This would he useful in an electronic blackboard application for a large class. ~

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The program was difficult for the novice, hut after a n appropriate apprentice period (15 min for some, an hour or more for others) it was friendly t o the user. I t provided a level of understanding of Lewis structure concepts that would not he attained by most students on their own with paper and pencil. The program is versatile, well-organized, well-documented, and will serve as a valuable teachine aid for instructors usine a variety of teaching techniques. Students may he seduced into learning some chemistry. William P. Jensen South Dakota State University Brwkings, SD 57007 Review II This program is described as having "interactive drill oroblems with answer evaluation and online help"and "short review tutorials on l.rwis diagrams and formal charge." Roth are accurate descriptions. The tutorials are essentially page-turning, hut with the text presented in short units and with appropriate diagrams. Both tutorials are concise, accurate, and helpful, deserihing how to draw Lewis structures and how to calculate the formal charees. The method given asks students to learn the standard honding patterns ior the rrprescntatirr rlrments (four bonds to carbon, three bonds and one lone pair far nitrogen, two honds and two lone pairs for oxygen, etc., in neutral molecules), fill in the honds and then add lone pair electrons to finish the structure. While one may quarrel with details of the presentation, (personally, I prefer to calculate the number of bonds reouired from the elertronr nvallahle and the electrons needed fur isulated atuma wlth complete octets) there are no serious prohlems with it. The tutorials do not allow for backing up or jumping around; hut are short enough (1215 screens) that this is not a serious drawback. No paper documentation is needed for student use of the program. The autoexec file automatically loads the program on hooting and from that point on all instruetions needed are on the screen. The only preliminary instruction needed for students is the location of the ENTER, ESC, shift, and cursor arrow keys and how to insert the disk and turn on the machine. After a problem is selected from the list of 48 presented, the student faces a mostly blank screen with elemental symbols, hond lines,and lone pair dots in different orientations in two columns on the left labelled with t h e appropriate keys for each (1 through 0, either alone or shifted, or alphabetic keys for the elemental symbols). The arrow keys move the cursor, and the appronriate elements can he nlaced as desired. ~ h e d i r p l a yislarge,with;lj high by 10wide grld for placement of elemental symhnls, hmds, or h e parrs. All students fuund that learning to use the graphicseditor wasquiek and easy. The program allows interruption of the editing operation a t any time to check out the charts (periodic tahle, standard hond patterns) avklahle for help, stopping the editine to eet an evaluation and hints on how to proceed, or stopping to switch to another problem. When a problem is completed (or the student wants to quit), the ENTER key is pressed and the program checks the result. I t ignores unusual placements of atoms,

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concentrating on the essential Lewis features (2 electrons on hydrogen, 8 electrons sround every other atom, proper arrangement of bonds, best structure from formal charge considerations). If correct, it proceeds to the next problem or allows selection of a new starting prohlem. If incorrect, it provides hints based on each of these criteria and then goes hack to the editor for further work. The periodic tahle and charts of probable hond arrangements of atoms in neutral molecules or oositive or neeative ions ran he called up at any time. A rprord is kept of successful solutams, hut n u of pwhI e m attempted. This record can be printed out a t the end of asession for student use or to he handed in as evidence of successful use of the program. The program was tested on old IBM-PC's (64K motherboard) and on a Zenith 158 with no prohlems.'~oloris advantageous, but not essential; the graphics display is easily read on CGA monochrome graphics. The students were freshmen who had worked with Lewis diagrams before, hut were not proficient in drawing them. No formal comparison between those who used and did not use the programs was made due t o time and equipment limitations. About 10 of 60 in the class chose to use the programs and thought it was helpful. After reading through the tutorials (15-30 minutes, depending on their reading speed and hackground knowledge), they worked 5-10 problems in 30-45 minutes with little or no assistance. Mechanics of the program are handled very well. I t is fast, with only minor waits during the tutorials and checking of answers. Errors in typing are simply ignored hv the oromam. .. . and none of the testers could hang the program Thedmplay is ea4ly read hy two or three students, in case group work is necessary or desirable, and color is used well (although it is not essential). The program does not use audio, so it does not distract others nearby. No knowledge of computers heyond use of the shift keys, and the enter, control, andescape keys is needed. The oromam .. oromots for the ODtrons availahb, and they are clear and unambiguous. It cannot he modified o r lirted (and is copy protected by having key di.k information written as data) hut can easily he used in different contexts. Two limitations should he noted, however. One approach to drawing the diagrams is presented, asking students to memorize the charts of orohable structures (four honds t o carbon, three honds and one lone pmr for nitrogen, two bonds and twu h e p a n for oxygen, etc.). Other approaches can he presented by the instructor hut are not supported by the program. In addition, all the ~roblrmsfitthestandardoctet rule, wlth no indication that expansion beyond 8 eleetrons may he necessary. When a student-drawn structure is wrong, a succession of hints is given. First the total number of electrons and the number around each atom is checked, then the overall geometry (not shape, hut which atoms are bonded t o which other atoms), and finally formal charge. If all are wrong, the program gives all t h e suggestions with enough delay for easy reading and then waits for input before stopping, returning t o t h e editor, or displaying t h e reference charts. The only assistance needed by the students came a t this point, when they could not think of a different geometry or

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arrangement of bonds to try. Although the brief, hut helpful, comments come from a fairly short list, they give the impression of being tailored t o the specific case. Some examples are-("Sorry, that's not right. The arrangement of atoms is incorrect."; "It fits the Lewis rules, but you can do better. Reduce formal charges."; and "There is one atom with more than 8 electrons." We found no errors in the chemistry or in the operation of the program. Overall, i t is a good program, with the programming and the chemistry welldone. I t does not present any new approaches or special pedagogic values beyond interactive drill, hut it has no intention to do so. Student reaction was favorable; no comparative statistics were taken comparing those who did and did not use the program, hut those who used i t thought it useful and very easy to use with no assistance. Donald A. Tarr St. Oiaf College Ncflhfieid,MN 55057

Improving s a 6 t Y In t h e Chemical Laboratory Jay A. Young, Ed. Wlley: New York. NY. 1987, xviil 350 pp. Figs. and tables. 17 X 24 cm. $45.00.

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This good hook opens with the editor's statements of his first and second laws of safety, their corollaries, and a conclusion that reads: 1. By eliminating the causes of close calls and nonevents, accidents will he eliminated. 2. If we learn how to identify that a close call or nonevent has in fact happened, we can then know that there was a cause. or causes, which can he identified. 3. Once identified, a cause can he eliminated. The hook brings together 19 leaders in the field of chemical health and safety with their specific "how to's" t o improve safety in the laboratory. Some readers in our colleges may be intimidated by the stated organizational structure with a vice president for safety, hut all will agree with the precept that a sound safety program begins with sunoort a t the hiehest manaeement level in the institutim. There must be a sratrment d purpose for the safety program and its chain of command. This first edition is marred by careless proofreading. (No errors were found that interfered with the message.) Also, there are same disconcerting quantitative differences between the major chapter on fume hoods and a chapter on handling hazardous research chemicals that also covers the use of hcmds.The h e r carries the misinformation rhnt OSHA enli,rees an early rule calling for exhausr rates of 125-150fpm when handling regulated carcinogens in la1,oratory hoodc. This chapter doesn't recognize the wrll rstlrbliihed evidence that such high rxhnust rates may provide poorer containment because of turbulence and that well-desiened " svstems will orovide effective orateetion a t

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importance.) The chapter fails t o define clearly the good practices essential for work-

er safety whatever the exhaust rate. Despite such flaws the hook is essential. reading for all workers in laboratories handling chemicals and for the administrators responsible for these facilities. It promises to become the American Standard for lahoratory practice. Malcolm M. Renfrew Univenity of Idaho MOSCOW. ID 83843

Contemporary Classics In Physical, Chemlcal, and Earth Sciences Arnold Thackray (Compiler), iS1 Press: Philadelphia. PA. 1986. xviii 375 pp. 15 X 23 cm. $39.95.

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In 1977 Eugene Garfield, founder and president of the Institute for Scientific Information (iSi), began publishing in CUTrent Contents (CC) t h e feature "This Week's Citation Classicn-an invited 500word commentary by the author of a Citation Classic, which is a seminal scientific paper as shown by its frequency of citation in papers by other scientists. To date 2,300 of these autobiographical commentaries have appeared. In these the authors describe their research, its genesis, and the circumstances that affected its progress and publication, and they include the type of personal details rarely found in formal scientific publications, such as obstacles encountered and side paths taken. They also speculate on the reasons for the frequent citation of their work. The volume under review here is the fifth in the "Contemoorarv Classics in Science" series (Eueene ~~.~' ~ a r i e l d . Editor-in-Chiefl ~~. and inrludes commentaries selerted from those published in CC/lJh~sical.Chernzial, and Eorrh Scwneea from 1979 to 1981. The one-page commentaries take the reader hehind the scenes of science as the authors describe where new ideas come from, how scientists interact with their colleagues and superiors t o produce outstanding results, what their personal motivations were in conducting specific projects, and which types of research environments consistently produce effective results. The chemistry section (132 pp.) consists of 6 chapters-basic concepts (24 commentaries), inorganic and organometallic chemistry and catalysis (16 commentaries), organic chemistry, hiochemistry, and chromatographic methods (21 commentaries), spectroscopic methods (15 commentaries), nuclear magnetic resonance (24 commentaries), and structural chemistry, analytical chemistry, and the physical properties of polymers (18 commentaries). Among the familiar classica are Ahrland, Chatt, and Davies' a and b acceDtor classification (1958). Pearson's hard and soft acids and bases (1963), Pimental and MeClelland's book an the hydrogen hond (1960), Bent's valencehond structures and hybridization in firstrow elements (1961). Jannik Bjerrum's hook on metal ammine formation (1941), Gillespie and Nyholm's VSEPR theory (1957), and Stahl's thin-layer chromatography (1958). Incidentally, the sixth volume in the series, "Contemporary Classics in Engineerins and Aoolied Science." also contains citation classici in chemirnl engineermg and fluid dynamics ( 3 5 wmmentsrws, and ~

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chemistry (38 commentaries), same of them duplicating those in the volume reviewed here. The concise, anecdotal commentaries contribute to future historiography by preserving important hut otherwise unavailable biographical and story-hehind-thestory information. Practicing chemists and chemical educators reading them will learn. of unfamiliar aspects of otherwise familiar classic research. This volume should demonstrate to both students and laymen the nature and methods of science and the excitement a t the cutting edge of scientific discovery. In the words of historian of science Gerald Holton, who wrote the foreword, "There is not only much t o ponder here for any consideration of realistic theories of progress in science; there is also pleasurable reading that would he most instructive if assigned to beginning graduate students who, through those scientific papers themselves, would never find out the marvelous range of empowering tools nature offers its attendants." George 0 . Kauffman California State University. Fresno Fresno. CA 93740

lntroductlon t o General, Organlc, a n d Blologlcai Chemistry Sally Solomon. McGraw-Hill: New York, NY, 1987. xiv 845 pp. Figs. and tabies. 20.8 X 26 cm. $38.95.

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The minute one opens Introduction to General, Organic, and Biological Chemistry, it is clear that its emphasis is different from that of the usual text directed toward students in the allied health fields. Neither the inside front cover nor back cover contains a periodic tahle or tahle of atomic weights! Rather, the inside front cover conb i n s a two-page table entitled "Caloric Value, Composition, and Vitamin and Mineral Content of Common Foods", and the inside hack cover contains two tables: "Sources and Deficiencies of Vitamins and Minerals" and "Vitamin Content of Vitamin Supplements". The periodic tahle and aeeompanying tahle of atomic weights are found on the hack side of the tahle "Sources ." a t the rear of the hook. There are a total of 28 chapters with the material divided about equally between general, organic, and hiochemistry. Perhaps the author's statement in the preface sums up this hook heat: "Throughout this text the excitement and usefulness of chemistry are conveyed by making clear connections hetween chemical principles, the surrounding world and the human body." As a professor who has many times taught the first semester of our two-semester sequence for allied health students, I will give some examples of this application t o the human body taken from the chapters on general chemistry. In chapter 1 (Measurement) we find a discussion and a figure that illustrates a urinome-

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(Continued on page A274) Number 10

October 1988

A273