Friendly Chemistry Teaching Tips for Lesson 15: Compounds with Polyatomic Ions Game Plan: A. Review polyatomic ions introduced in Lesson 14. B. Introduce formation of complex compounds by reading lesson text together. Use ion flashcards to demonstrate compound formation. C. Play Compound Football. D. Play Teamwork—Compound Formation version. E. Assign Practice Pages. F. Give Lesson 15 test. A. Review polyatomic ions introduced in Lesson 14. Begin class today by reviewing the many polyatomic ions learned in the last lesson and how ions join to form compounds from previous lessons. B. Introduce formation of complex compounds by reading lesson text together. Use ion flashcards to demonstrate compound formation. Read text together emphasizing, like compounds with monoatomic ions, the charges of each compound constituent must add to zero. Require that your students utilize parentheses to isolate the polyatomic ions within the compound. For those students who are not familiar with the addition of positive and negative numbers, utilize the ion flashcards to show how the polyatomic ions form compounds. Instructions for this option can be found in Lesson 13. In this lesson, you will use the entire ion flashcard set.. 233 Friendly Chemistry Cation Playbook Anion Playbook Sodium ion Fluoride Lithium ion Chloride Potassium ion Iodide Hydrogen ion Bromide Magnesium ion Oxide Calcium ion Sulfide Barium ion Examples of Anion and Cation Playbooks—note these use very simple ions. You will add more complex ions as your students learn the game. ~ 40 feet Scrimmage Line Safe Zone for Anions ~ 20 feet Huddle Area for Anions Position yourself here during play. Playing area for Compound Football Game 234 Huddle Area for Cations Safe Zone for Cations Friendly Chemistry C: Play Compound Football! (a.k.a. Rock, Paper, Compound) This game is a very active game which can provide many, many opportunities for your students to practice the mental formulation of compound formulas. Begin by dividing your students into two teams. Because the membership of each team will continually change throughout the game, it is not necessary to divide according to ability or size. A team captain should be chosen from each team - we usually appoint the oldest team member to be the captain. One team should be designated as the Anions and the other the Cations. Each team captain will be provided with a team “playbook” which lists ions that can be used during play. The Anion team captain should receive the Anion Playbook while the Cation team captain should receive the Cation Playbook. Prepare these playbooks in advance by choosing ions that you would like your students to be able to recall from memory. Any of the monoatomic ions could be included, and as your students become better acquainted with the polyatomic ions, consider adding those to their playbooks as well. Samples of playbooks are on page 234. Choose an outdoor playing area if possible at least 20 by 40 feet. Use flags or poles to mark the boundaries of the playing area. A scrimmage line equidistant from either end of the playing area should also be marked (use flour to mark this line if digging a line into the turf is not acceptable!) Refer to page 234 for details on the playing field. An indoor gym works equally well. Play begins by having each team captain gather his or her teammates into a huddle near their team’s safe zone. While in the huddle, the team chooses one ion from their playbook for the upcoming play (the term ‘play’ being used as in a ‘football play’). Once each team chooses its ion, players line up along the scrimmage line facing each other like lineman on a football team. You will serve as the referee and locate yourself on one end of the scrimmage line. To initiate the current play, give a football cadence like, “Hut, hut, go!” On the word “go” both teams yell the name of their chosen ion (the Anions yell-out their anion and the Cations yell-out their cation). What happens next depends upon the ratio required of each ion to create a stable compound. If the compound made by the two chosen ions can be made by a 1:1 ratio (i.e. one atom of each ion), the Cations are 235 Friendly Chemistry in control and chase the Anions who, in turn, quickly retreat to their safe zone. If a Cation team member tags an Anion team member, the Anion team member becomes a Cation team member for the next play. Anion team members who reach their safe zone untagged, remain on the Anion team for the next play. Should the ratio of chosen ions required to make the compound NOT be a 1:1 ratio, the Anion team is in control and they chase the Cations who, in turn, retreat to their safe zone. Tagged Cations become Anions and play continues. With each play, team members are exchanged until one team eventually gets “wiped-out.” If a team dwindles too early, stop play and re-align the teams so that play can continue. Below are some possible scenarios to help you better understand how this game is played. Suppose the Cation team chooses the sodium ion for its play while the Anion team chooses fluoride. Both teams come to the scrimmage line and, following your cadence, each team yells its ion and the play unfolds. Because sodium and fluoride create a compound with a 1:1 ratio, the Cations are in control of the play and they chase the Anions who retreat to their safe zone. Tagged Anions now become Cations and teams huddle for the next play. Suppose for a second play, the Cation team chooses the calcium ion while the Anion team chooses chloride. Both teams come to the scrimmage line and, following your cadence, each team yells its ion and the play begins. Because calcium and chloride do not form a compound in a 1:1 ratio (calcium chloride is Ca 1Cl2 - a 1:2 ratio), the Anion team is in control of the play and chase the Cations who in turn retreat to their safe zone. Tagged Cations become Anions and both teams huddle for the next play. The key is that if the ratio of ions is 1:1, the Cations are in control and do the chasing. If the ratio is anything but 1:1, the Anions are in control and they do the chasing. If you find your students confused and not sure when to chase or run, point in the direction of the safe zone where team members should run. For example, if the Cations are in control of a play, assist all involved by pointing to the safe zone of the Anions so that the Cations will know to chase and the Anions will know to run to their safe zone. Eventually, your students should be able to mentally formulate the compound formula and know when to run or chase without your assistance. As noted earlier, add more and more ions to each team’s playbook for added practice of 236 Friendly Chemistry compound formulations. We have tremendous fun playing this game. The momentary chaos that inevitably ensues once a play gets underway can be quite amusing. Many times a team will retreat just because one member chooses to run only to realize a few seconds later that they are in control of the play and should be chasing the opposing team! If you find it difficult to hear the ions being played, you can have your team captains whisper their team’s choice of ion to you before lining up at the scrimmage line. This will enable you to assist your students in which direction to run. Because a team captain is just as likely as any other player to be tagged during play, the oldest “surviving” team member assumes the duty of team captain and play continues. After each play, confirm with your students the correct compound formula so that all students are correct in their mental formulations of each compound. You may play Compound Football with younger students who may not have memorized many of the ions by making the following game modifications. Instead of playbooks, position a table (a card table works well) near the safe zone for each team. Make sure these tables are not in the path where your students may be running. Separate a set of ion flashcards into anions and cations and then take one of each type of card to make a set of cards for each team. On the table nearest the Cation safe zone, spread the cation cards across the table. Do likewise with the anion cards on the Anion table. Instead of huddling on the playing field, instruct your students to huddle around the card tables. When in the huddle, the players should choose an ion for the next play. The captain should then take the chosen card and hiding it in his or her hands or shirt/jacket join his or her teammates at the scrimmage line. After the cadence, each team yells their ion and the captains reveal the chosen cards to opposing team. Play continues the same as in the initial variation described above. When your younger students gain confidence using the ion cards, encourage them to leave the chosen card on the card tables before they line up on the scrimmage line. Eventually, suggest using a playbook as described above. A final variation which works well when students have learned several of the ions is, instead of allowing your students to pick their plays, is to have all team members line up across from each other on the scrimmage line and you call out a compound 237 Friendly Chemistry name. Depending up the ratio of cation to anion, play continues as above. D. Play Teamwork—Compound Formation version. The Compound Formation Version of Teamwork is a great way to give your students tons of practice at writing compound formulas using the entire set of ions. For this version, persons at the table farthest from you are asked to write the cation symbol and charge. They pass their paper to persons at the next table forward who, beside the cation, write the anion. Each team then passes their paper forward to the table nearest you where the correct subscripts are added to make the stable compound. The paper is then passed to you for checking. Like the other Teamwork versions you have played in past lessons, the first team to provide you with the correct compound formula for the compound name you called, earns two points for their team. Other teams with papers arriving correct, but later, earn one point for their team. Papers with errors get sent back to the table where the errors were made. Teammates can identify errors from other tables, but cannot fix them. Using different colored pens or markers at each table insures no one “helps” when not appropriate. Play 3-4 rounds and then rotate your students to new tables. Team points may be earned as bonus points on later quizzes or tests at your discretion. E. Assign Practice Pages. F. Give Lesson 15 test. 238 Friendly Chemistry NAME_______________________________________ DATE___________________ FRIENDLY CHEMISTRY Lesson 15 Test Forming Compounds from Polyatomic Ions Write the correct compound formula for each compound name listed below. Compound Name Compound Formula Compound Name 1. barium hydroxide 11. calcium sulfite 2. calcium nitrate 12. strontium carbonate 3. ammonium sulfate 13. lead (II) hypochlorite 4. mercury (II) chlorite 14. chromium acetate 5. aluminum phosphate 15. potassium permanganate 6. silver oxide 16. magnesium chlorate 7. copper (I) cyanide 17. nickel sulfide 8. potassium sulfite 18. lithium chromate 9. hydronium nitrite 19. ammonium dichromate 10. hydrogen peroxide 20. aluminum perchlorate 239 Compound Formula Friendly Chemistry Write the correct compound name for each formula given below. Formula Compound Name Formula 21. Na(NO3) 26. Pb+2(Cl)2 22. Ba(CO3)2 25. Zn(ClO4)2 23. K(MnO4) 28. Ca(CN)2 24. Mg(SO4) 29. (NH4)2O 25. Ni(ClO3)2 30. Al(OH)3 240 Compound Name Friendly Chemistry Lesson 15: Making Compounds with Polyatomic Ions Forming compounds with polyatomic ions is very similar to the way monoatomic ions form compounds. You must remember that the polyatomic ions (although made of more than one individual element) function as one unit. The charge given to the polyatomic ion is for the whole ion and not any individual portion. Let’s look at some examples of how compounds made with polyatomic ions form. Sodium hydroxide is a compound commonly known as lye which is used to unclog drains and to make lye soap. The ions which make sodium hydroxide are the cation sodium and the anion hydroxide. Sodium Na+1 Hydroxide (OH)-1 241 S135 Friendly Chemistry To make the compound sodium hydroxide, we would need to use one sodium ion and one hydroxide ion. In doing so, the sum of the charges equals zero. Recall, also, that it is customary to write the cation first, followed by the anion. Na+11(OH)-11 Note that one sodium ion can bond with one hydroxide anion to form sodium hydroxide. Let’s look at some more examples. Calcium carbonate is the chemical which makes up the shells of many ocean creatures. Another name for fossilized calcium carbonate is limestone. The constituents of calcium carbonate are the calcium cation and the carbonate anion. Calcium Ca+2 Carbonate (CO3)--2 In order to make the compound calcium carbonate, the charges of the ions must add up to zero. In this case, using one atom of each ion will result in a total charge of zero. Ca+21(CO3)--21 Note that one calcium cation can bond with one carbonate anion to form calcium carbonate. Here is another example. Hydrogen peroxide is a well-known antiseptic solution used to “bubble-out” impurities in shallow wounds. The hydrogen peroxide compound is composed of the hydrogen cation and the peroxide anion. Hydrogen H+1 Peroxide (O2)-2 If we take one hydrogen cation and one peroxide ion, the sum of the charges S136 242 Friendly Chemistry does not add up to zero. We must take a multiple of one or both of the ions in order for the sum of the charges to equal zero. In this case, taking two hydrogen cations (each with a +1 charge) and one peroxide anion (with its -2 charge) will result in a total charge of zero. H+12(O2)-21 Note that it takes two hydrogen atoms for each peroxide anion to create the stable hydrogen peroxide compound. And here is a final example. The chemical formula for rust is iron (III) oxide. The iron (III) oxide compound is composed of the iron (III) cation and the oxide anion. Recall that ions with a Roman Numeral as part of their name, tell you the charge of the cation. In this case iron (III) is Fe+3. Iron (III) +3 Oxide O-2 Fe Forming this compound is a little more challenging. In order to get our charges to add to zero, we must take two iron (III) cations and three oxide cations. Fe+32 O-23 Note that it takes two iron (III) cations along with three oxide anions to form rust! Practice making compounds by completing the practice pages which follow. 243 S137 Friendly Chemistry Name_________________________________ Date___________________ Friendly Chemistry Lesson 15: Compound Writing Practice Below you will see a list of compounds. Write the chemical formula for each compound. Refer to your Master Ion List or flashcards if necessary. Compound Name S138 Chemical Formula Compound Name 1. Sodium chloride 21. Barium hydroxide 2. Potassium nitrate 22. Calcium nitrite 3. Lithium chloride 23. Cesium sulfate 4. Barium sulfite 24. Nickel nitrate 5. Calcium carbonate 25. Calcium oxide 6. Strontium oxide 26. Sodium bromide 7. Tin (IV) sulfate 27. Silver chromate 8. Hydrogen chlorate 28. Copper (II) fluoride 9. Potassium perchlorate 29. Potassium permanganate 10. Aluminum acetate 30. Lithium carbonate 11. Magnesium sulfite 31. Nickel cyanide 12. Mercury (II) bromide 32. Lead (II) hypochlorite 13. Sodium dichromate 33. Zinc chlorite 14. Strontium iodide 34. Hydrogen peroxide 15. Ammonium dichromate 35. Copper (I) sulfite 16. Potassium chloride 36. Hydronium sulfide 17. Chromium perchlorate 37. Nickel phosphate 18. Calcium cyanide 38. Mercury (II) carbonate 19. Barium chlorite 39. Tin (IV) sulfate 20. Ammonium chloride 40. Potassium hydroxide 244 Chemical Formula