METALLIC BONDING

1. METALLIC BONDING Büşra AÇIKEL Gamze KARACA Azize ŞEN

2. Lesson Plan • Grade level: 10thgrade • UnitNumber: 3 • Unit: ChemicalSpeciesandTheirInteractions • Topic: MetallicBonding • Allocated time: 2 x 45 hours = 90 minutes

3. Learning Outcomes • Explains the formation of metallic bonding. • Make connections between the structure of metallic bonding and the properties of metals.

4. Prerequisities • The structure of atomic model (Valence electrons) • Chemical species ( metal, nonmetal) • Delocalized electrons • The mechanism of bonding (Ionic bonding)

5. Concept List • electrostaticattractions • sea of electron • metallicbond • alloys • malleability • ductility • electricalconductivity • thermalconductivity

6. Materials Needed • 10 – 15 balloons • Experiment: beher glass, silverplate, copperplate, ironplate, iceand hot water • videosandanimations

7. 1ST LECTURE HOUR ( 45 min.)

8. INITIATION ( 7 min.)

9. Entrance • Greeting • Because balloons take the student’s attention we preferred to start with a student activity before reminding previous lesson • Attendance while making student activity to prevent time consuming

10. Balloon Activity

11. Balloon Activity( 5 min.) • Before explaining the aim of the activity, let us explaining the activity in order to make it meaningful for you in understanding our aim. • Balloonactivity: • Givestudentsinflatedballoons. • Each of thestudents is an atom of some metal.(e.g. gold) • Each of theballoon is an electronbelongingtothat atom. • Eachstudenttosses her/his electronfreelyfromhandtohandintotheairandgentlyhitsotherelectronsthatare in theair, muchlike a volleyballgamewithmanyballoonsbeingusedinstead of oneball. • Everybodywantstoplaywiththeballoons, sothiskeepstheatomstogether.

12. Aim of the Student Activity • This activity will serve as an analogy for metallic bonding • At the end of the first lecture students will make connection between metallic bonding and the balloon activity.

13. During Activity • While giving balloons to students, they probably wonder why teacher let them playing with balloons and so, teacher says: “ We will make a connection between our topic and this activity at the end of the lecture.” • During the activity teacher won’t make any extra explanation about the aim of this activity

14. The Topic • After finishing the activity, teacher says: “ We know how metal and nonmetal come together, we learned how nonmetal and nonmetal come together; what about metal and metal?” • Theaimof this question is not really asking students to explain their ideas but just informing students about what will they learn in this lecture roughly.

15. MAIN BODY ( 30 min.)

16. Review of the last lesson(10 min.) • Afterinformingstudentsaboutthetopic, teacherstartswithreview of thelastlesson • Aim: remindingionicbondingforms a basisforbetterunderstanding of metalicbonding. Becausecomparingmetallicbondingwith a type of bondingthatstudentsarefamiliarwithprovidesstudentswithmakingconnectionsbetweennewandoldknowledge.

17. Review of the last lesson(10 min.) • Teacher says “Let’s remember what the ionic bonding is first to understand metallic bonding better.” • Teacher asks “ Do you remember how does ionic bond form?” Expectation: We expect students to remember: • metal~ nonmetal • “e-” transfer because of octet rule • “+” and “-” ion formation

18. Review of the last lesson(10 min.) • If students can not remember, teacher asks some guiding questions: • metal~ nonmetal: “ Between which kinds does ionic bonding formation occurs?” • octet rule/ “e-” transfer  “+” and “-” charges: “We know that elements are found as their most stable forms in the nature. For example O is seen in the form of O2. So, do you remember how an element become more stable?”(sharing/ transfer of e- (*) )

19. Video: Ionic Bonding • After taking students respond, teacher says: “ Let’s see a video simulation showing the formation of ionic bonding.” • Video (Ionic Bonding) • Teacher makes explanation while showing video.

20. Ionic Bonding --> Metallic Bonding • As you know metals are tend to give their valence electron instead of taking more electron So, they tend to be “+” charged. • Teacher asks: “ How do you think that metals and metals form a bond?” “ How do they look like?”

21. STUDENTS’ MISCONCEPTIONABOUT METALLIC BONDING

22. MISCONCEPTIONS ABOUT THE STRUCTURE OF METALLIC BONDING • Cations without mobile electrons • Unique motion of atoms with their corresponding electrons( atoms and their corresponding electrons move together such that its electrons move only in a certain place) • In metal the electron are covalently bonded (Taber 2003) • Metals have bonding similar to ionic because there is positive and negatives (Taber 2003) • There is no bonding in pure metals (Taber 2001)

23. “Whyatoms of metals do not repeleachotherwhileallarepositivelycharged? / How can atoms of metalsstaytogetherwhiletheyarepositivelycharged?” IONIC BONDING METALLIC BONDING

24. Possible Students’ Predictions Teacher writes the predictions on the board: • It can’t be possible • They can stay together via attraction • They can stay together with the help of electrons

25. Sea of Electron • 00.00 – 00.27 ( Sea of Electron) • Strong side: We preferred this animation because it was the only simulation that shows the movement of both electrons and cations • Weak side: It is not clear whether the electrons are valence electrons or both inner and outer electrons

26. Teacher Explanation • an array of metal cations in a "sea" of valence electrons

27. Teacher Explanation • The electrons are confined to the metal by electrostatic attractions to the cations, and they are uniformly distributed throughout the structure

28. Teacher Explanation • The valence electrons are mobile, and no individual valence electron is confined to any particular metal ion

29. Alloys • Teacher says “We learned the structure of metallic bonding within metal” “Can we form a substance composed of two different metals?” Expectation: We don’t expect students to give detailed explanation. But some students will probably heard about alloys before from daily life.

30. Alloys • Teacher says: “Have you ever heard about bronze medal from olympiads?” Expectation: Students probably say yes.

31. Alloys • Coin • Steel (Iron- Manganese and some other elements) • Brass( Copper- Zinc) • Pewter ( Lead- Tin)

32. Alloys • “These are called as alloys and alloys are mixture composed of at least 2 different metals.” • All ingredient substance are melted separately then mixed while they are liquid in certain amounts. • When they get cooler they become homogenous solid.

33. CLOSURE ( 8 min.)

34. Analogy (Baloon Activity) • Aim: • Providingstudentswith a chance of explainingthemetallicbondingwiththeirownwords. • Toassessstudents’ level of understandingwithinthelesson. • At theend of thefirstlecture, teacherasksstudentsto define thesimilaritiesbetweenmetallicbondingandthisactivity.

35. Analogy (Baloon Activity) • Teacherasks: “How can wemakeconnectionbetweenmetallicbondingandbaloonactivity in thelight of thingsthatwelearned?” Expectation: • We expect students to explain that they represent some atoms of metal • We expect students to explain that balloons represent electrons belonging that atoms • We expect students to explain that moving balloons resemble the sea of electron in the metallic bonding.

36. Analogy (Baloon Activity) • If students are not able to see the similarities between metallic bonding and balloon activity we will ask more guiding and specific questions: “What may balloons represent in the balloon activity in terms of metallic bonding?” “What may students represent in the balloon activity in terms of metallic bonding?”

37. 2ND LECTURE HOUR ( 45 min.)

38. INITIATION ( 5 min)

39. The Topic • Teacher says: “ We learned the structure of metallic bonding.” “ So, What can be the properties of metals regarding of the structure of metallic bonding?” Expectation: The aim of this question is informing students about the topic of the lesson.

40. MAIN BODY ( 30 min.)

41. Malleability • 03.42 – 05.10 ( Metallic Bonding youtube) garipkonusanadam

42. Malleability • As you see the atoms were shifting, did not break apart. • “Why would it that be the case?” • Because the delocalized electrons are always there. • Any shifting positively ions are going to be hold together by attraction to the constant presence of those valence electrons that sea of electrons • Delocalized electrons: Electrons belonging to certain molecules are not attached to a particular atom or bond in that molecule. These electrons are said to be "delocalized" because they do not have a specific location (are not localized)

43. Malleability • Teacher asks: “ In where this property can be used in daily life?” Expectation: We expect students to give some examples of malleability from daily life because there are numerous examples from …. To a very complicated piece of an electronic mechanism.

44. Malleability

45. Ductility • Teacher asks: “What about a wire?” Expectation: Students will again probably think that it is because of malleability. • Teacher says: “ But can we get a wire by applying compressive force on a metal?” “ What other kind of force can be applied on a metal to get a wire?” Expectation: We don’t expect students to answer these questions. We just want make them thinking on. • Teacher says: “ Let’s watch a video to find answers of these questions.”

46. Video • 01.04 – 03.46 • Aim: Teaching ductility by comparing the malleability and ductility of a metal at particular level. • Strong side: It explains malleability and ductility at particular level. • Weak side: Sea of electrons are not represented at the mean while applying force

47. Ductility • Ductility is a solid material’s ability to deform under tensile force • After video watching, teacher asks:“ Which one the wires in the pictures represents the better ductility of a metal?”

48. Thermal Conductivity • As a 3rd property of metals we want to teach the thermal conductivity by an experiment. • Aim: to explain thermal conductivity by comparing the thermal conductivities of three different metals Ag, Cu, and Fe. • We intentionally choose 3 different metals because we will want students to write a journal about the reason of 3 different rates of thermal conductivities.

49. Thermal Conductivity Experiment • Activity will be done by grouping students. Each group will consist of 3-4 students. • Video of the experiment

50. Electrical Conductivity • Teacher says: “Another property of metals is electrical conductivity.” • Video simulation • “As in the thermal conductivity, the motions of delocalized electrons conducts the electricity as well.” • “Electrical current flows easily through the moving electrons in the sea of electrons.”