JCE Classroom Activity #113: An Interlocking Building Block Activityin Writing Formulas of Ionic CompoundsKristie R. Ruddick and Abby L. Parrill*

Department of Chemistry, The University of Memphis, Memphis, Tennessee 38152, United States

*S Supporting Information

ABSTRACT: An activity in which students use toy interlocking building blocks to buildrepresentations of ionic formulas is described. Students explore cation-to-anion ratiosusing interlocking toy brick-like blocks to represent trivalent, divalent, and monovalentcations and anions. Students who participated in the building blocks activity showedsignificantly higher posttest scores than students who had not participated.

KEYWORDS: High School/Introductory Chemistry, Inorganic Chemistry, Chemical Education Research,Hands-On Learning/Manipulatives, Nomenclature/Units/Symbols

FEATURE: JCE Classroom Activity

■ BACKGROUND

As a teacher of high school chemistry, one of us (K.R.R.) has triedvarious methods of teaching students to write formulas for ioniccompounds. Most textbooks teach the familiar “crisscross”method for writing chemical formulas.1 For years, K.R.R. has hadstudents create ion card cut-outs as described in an articlepreviously published in this Journal: “The Rainbow Wheel andRainbow Matrix: Two Effective Tools for Learning IonicNomenclature.”2 The rainbow matrix is an online game thatallows students to practice combining the correct ratio of cationsand anions to make neutral compounds. In attempts to capturestudents’ attention, teachers are always searching for fun ways torepresent chemical concepts. JCE Classroom Activity #43,entitled “LEGO Stoichiometry”,3 describes a lesson in limitingreagents in which students use a LEGO car kit as a way tovisualize the concepts. Likewise, in JCE Classroom Activity #99,“Clip Clues: Discovering Chemical Formulas”,4 a creative activityprovides a hands-on learning experience using paper clips inwriting formulas for ionic compounds. While toy building blocksand, specifically, interconnecting plastic toy blocks have beenused to illustrate various chemical concepts such as reactionkinetics,5 design of advanced materials,6,7 and simple elementsand atoms for lower grade students,8,9 this activity uses LEGObricks to teach ionic formulas. LEGO blocks provide excellentrepresentations of ions, particularly because the blocks are colorcoded, and the valency of the ion can be represented by thenumber of “dots”, or raised knobs, on a brick. For example, a blue1 × 3 brick (1 dot wide and 3 dots long) can represent cationicAl3+. The oxide ion, O2−, can be represented by a red 1 × 2 brick(1 dot wide and 2 dots long) (Figure 1). These two types of

bricks can then be assembled to make a product that helpsstudents determine the cation-to-anion ratio in aluminum oxideand write the chemical formula (Figure 2).

■ ABOUT THE ACTIVITYIn this activity, students build LEGO models of ionic chemicalcompounds. Students may use real LEGO bricks or virtual ones ifthe freely available LEGODigital Designer10 software is installed

Published: September 19, 2012

Figure 1. LEGO brick “dots” (raised knobs) represent valency of theion. The blue 1 × 3 brick represents the aluminum cation with a +3charge. The brick is one dot wide and three dots long to represent thecharge. The red 1 × 2 brick is one dot wide and two dots long torepresent the oxide ion.

Activity

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on a computer. Students can use the software to complete theentire activity (Figure 2). While in this study the students usedreal LEGObricks, K.R.R. has used LEGODigital Designer10 overthe LCD projector to introduce the activity to the class.Students follow three rules as they build their models:

1. Trivalent, divalent, and monovalent ions are representedwith 1 × 3, 1 × 2, and 1 × 1 bricks, respectively.

2. Cations are blue. Anions are red.3. Neutral formula units are rectangular using the lowest

whole number ratio of bricks. All blue bricks must beplaced in a single row in the final rectangular product, andlikewise for the red bricks.

As an example problem, students are asked to build a LEGOmodel of aluminum oxide. Because Al is a trivalent cation, Al3+, itis represented with a blue 1 × 3 brick. Oxide is a divalent anion,O2−, and is represented with a red 1× 2 brick. To create a neutral(rectangular) formula unit, we need 2 blue 1× 3 blocks and 3 red1 × 2 blocks. The formula is thus Al2O3 (Figure 3). Thesubscripts in the formula are determined by the number of eachtype of brick used. Students write the formula and the number ofbricks used in a data table.

■ INTEGRATING THE ACTIVITY INTO THECURRICULUM

This activity was introduced to chemistry students in an inner-city high school where it was used as a fun introduction tochemical formulas. As a mastery of chemical formulas isnecessary for success in understanding chemical reactions, thislesson should be taught immediately before the concepts of

molar mass, balancing chemical equations, and stoichiometry. Adiscussion of ions (monatomic and polyatomic) should precedethis activity. Be sure to discuss how to deal with transition metals,which need parentheses and roman numerals as illustrated byFe(II) sulfide and Fe(III) sulfide. Students were directed to atable of polyatomic ions in their text. Be sure to follow-up thisactivity with a brief discussion of crystal lattices in order not togive the misconception that ionic structures are as simple as theseLEGOmodels. The students should bemade to realize that theseare the lowest whole number ratios of cations to anions (formulaunits).Teachers can purchase enough LEGO bricks to complete this

activity (12 sets) for less than $20 at the LEGOWeb site,11 usingthe category “bricks” and the individual color “red” or “blue”. Youcan scroll down to locate 1 × 1, 1 × 2, and 1 × 3 bricks. Studentswill need three of each type of brick (1× 1, 1× 2, and 1× 3) bothin blue and red, for a total of 18 bricks per pair of lab partners.The LEGObricks can be preassembled for distribution to pairs ofstudents as shown in Figure 4. Students should be directed to

return the bricks after the activity in the same fashion as theyreceived them. The student directions in the SupportingInformation instruct the students to show the teacher theirmodel before moving on to the next model. You will want torequire that they get your initials to make sure they areperforming the activity correctly. With sufficient introductionand modeling by the teacher (with real bricks or using LEGODigital Designer and a projector) this activity requiresapproximately 30 min to complete.

■ ANALYSIS OF THE ACTIVITYThree separate classes in an inner-city school comprised threegroups of students. These classes were students in the sameschool taught by the same teacher during the 2010−2011 schoolyear. Data were collected in January 2011. One group of students(the conventional instruction group, N = 25) was taught writingchemical formulas using lecture-style presentation of thecrisscross method with no hands-on activities. After the lecture,students were assigned group work and homework. A secondgroup (the virtual game group, N = 13) played the RainbowMatrix game to learn how to write chemical formulas. Students inthe virtual game group were also given homework. The thirdgroup (the LEGO lab group, N = 14) participated in the LEGOactivity and also received the same homework assignment as theother two groups. Students in all three groups were administeredthe same 10-question, multiple-choice posttest. (See theSupporting Information.) The distribution of posttest scores(including outliers) for all three groups is shown in Figure 5.In addition, Figure 5 shows that students in the LEGO lab

group outperformed both the conventional instruction and thevirtual game groups. A significant difference in posttest scoresamong the three groups is seen using a one-way ANOVA test:F(2,49) = 4.18; p = 0.021. Post-hoc comparisons using theTukey−Kramer test for differences betweenmeans show that the

Figure 2. Screenshot from LEGO Digital Designer showing model ofaluminum oxide. LEGO and the Brick and Knob configurations aretrademarks of the LEGO Group of Companies, used here by specialpermission. Copyright 2011 The LEGO Group.

Figure 3. Brick model of aluminum oxide.

Figure 4. Preassembled LEGO brick set of 18 bricks (9 red and 9 blue)for easy distribution to lab partners.

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mean score for the LEGO lab group (M = 7.79, SD = 2.04) wassignificantly higher than both the conventional instruction group(M = 6.12, SD = 2.20) and the virtual game group (M = 5.77, SD= 1.48).However, the mean scores of the virtual game group and the

conventional instruction group did not differ significantly.Students had trouble with the Rainbow Matrix game owing tounfamiliarity with the software program. Student learning in thevirtual game group would require more class time for students tofeel comfortable using the program. Additionally, as Figure 6

illustrates, the LEGO lab group outperformed both the virtualgame group and the conventional instruction group for 8 out of10 test items. Note that the conventional instruction group islarger in size than both other test groups: the researcher hadaccess to these three classes and chose to assign the largest classto the conventional instruction group because of the lecture-stylenature of the activities associated with teaching the traditionalcrisscross method. The conventional instruction could have beenplaced at a slight disadvantage owing to its size, but note that theconventional instruction group performed comparably to thesmaller virtual game group. Additionally, the mean score of 7.79for the LEGO lab group is significant even without comparisonto other test groups. One reviewer pointed out that answer “a” forquestion 4 (Figure 7) includes “(III)” after “aluminum”, which istechnically not correct. This mistake could have resulted in therelatively low number of correct responses for this item.In conclusion, a fun, effective, and low-cost classroom activity

using LEGO bricks to model ionic formulas has been created andtested in an inner-city high school classroom. Students whoparticipated in this activity showed higher posttest scores than

did students who were taught by either a traditional lecture styleor using a virtual game available online.

■ ASSOCIATED CONTENT*S Supporting Information

Student activity worksheet; student activity worksheet answers;posttest. This material is available via the Internet at http://pubs.acs.org.

■ AUTHOR INFORMATIONCorresponding Author

*E-mail: aparrill@memphis.edu.Notes

The authors declare no competing financial interest.

■ REFERENCES(1) Tro, N. J. Unit 6. In Introductory Chemistry, 4th ed.; Prentice Hall:Upper Saddle River, NJ, 2011.(2) Wulfsberg, G. P.; Sanger, M. J.; Melton, T. J.; Chimeno, J. S. TheRainbowWheel and RainbowMatrix: Two Effective Tools for LearningIonic Nomenclature. J. Chem. Educ. 2006, 83 (4), 651−654.(3) Witzel, J. E. Lego Stoichiometry. J. Chem. Educ. 2002, 79 (3),352A−352B.(4) Carmen, F.; Mason, D. Clip Clues: Discovering ChemicalFormulas. J. Chem. Educ. 2008, 85 (12), 1648A−1648B.(5) Cloonan, C. A.; Nichol, C. A.; Hutchinson, J. S. UnderstandingChemical Reaction Kinetics and Equilibrium with Interlocking BuildingBlocks. J. Chem. Educ. 2011, 88 (10), 1400−1403.(6) Sharma, C. V. K. Designing Advanced Materials As Simple AsAssembling Lego Blocks! J. Chem. Educ. 2001, 78 (5), 617−622.(7) Lohmeijer, G. G.; Schubert, U. S. Polym. Chem. 2003, 41 (10),1413−1427.(8) Mind and Hand Alliance and MIT Edgerton Center. LEGOChemistry. http://web.mit.edu/edgerton/outreach/ACT_LC.html(accessed Aug 2012).(9) LaRosa, L. My Science Lessons Blog: A Collection of Ideas,Activities, and Lessons for Grades 5−8. http://mysciencelessons.wordpress.com/tag/atoms/ (accessed Aug 2012). (Scroll to the “LegoLab” entry posted on December 4, 2009 by mysciencelessons.)(10) LEGO Digital Designer Web Page. http://ldd.lego.com/(accessed Aug 2012).(11) LEGO Pick a Brick Web Page. http://shop.lego.com/en-US/Pick-A-Brick-11998 (accessed Aug 2012).

Figure 5. Box plot of posttest results.

Figure 6. Posttest scores by item for the three groups of students: virtualgame, LEGO lab, and conventional instruction.

Figure 7. Example posttest item, question 4, with its multiple-choiceanswer options.

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