METALLIC BONDING

Büşra AÇIKELGamze KARACA

Azize ŞEN

Lesson Plan• Grade level: 10th grade

• Unit Number: 3

• Unit: Chemical Species and Their Interactions

• Topic: Metallic Bonding

• Allocated time: 2 x 45 hours = 90 minutes

Learning Outcomes

• Explains the formation of metallic bonding.

• Make connections between the structure of metallic bonding and the properties of metals.

Prerequisities

• The structure of atomic model (Valence electrons)

• Chemical species ( metal, nonmetal)

• Delocalized electrons

• The mechanism of bonding (Ionic bonding)

Concept List

• electrostatic attractions

• sea of electron

• metallic bond

• alloys

• malleability

• ductility

• electrical conductivity

• thermal conductivity

Materials Needed

• 10 – 15 balloons

• Experiment: beher glass, silver plate, copper plate, iron plate, ice and hot water

• videos and animations

1ST LECTURE HOUR( 45 min.)

Drag picture to placeholder or click icon to add

INITIATION( 7 min.)

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

Balloon Activity

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.

• Balloon activity:

• Give students inflated balloons.

• Each of the students is an atom of some metal.(e.g. gold)

• Each of the balloon is an electron belonging to that atom.

• Each student tosses her/his electron freely from hand to hand into the air and gently hits other electrons that are in the air, much like a volleyball game with many balloons being used instead of one ball.

• Everybody wants to play with the balloons, so this keeps the atoms together.

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.

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

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?”

• The aim of this question is not really asking students to explain their ideas but just informing students about what will they learn in this lecture roughly.

MAIN BODY( 30 min.)

Review of the last lesson(10 min.)

• After informing students about the topic, teacher starts with review of the last lesson

• Aim: reminding ionic bonding forms a basis for better understanding of metalic bonding. Because comparing metallic bonding with a type of bonding that students are familiar with provides students with making connections between new and old knowledge.

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

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- (*) )

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.

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?”

STUDENTS’ MISCONCEP

TIONABOUT

METALLIC BONDING

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)

“Why atoms of metals do not repel each other while

all are positively charged? / How can atoms of metals

stay together whilethey are positively charged?”

IONIC BONDING METALLIC BONDING

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

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

Teacher Explanation

• an array of metal cations in a "sea" of valence electrons

Teacher Explanation

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

Teacher Explanation

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

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.

Alloys

• Teacher says:

“Have you ever heard about bronze medal from olympiads?”

Expectation:

Students probably say yes.

Alloys

• Coin

• Steel (Iron- Manganese and some other elements)

• Brass( Copper- Zinc)

• Pewter ( Lead- Tin)

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.

CLOSURE( 8 min.)

Analogy (Baloon Activity)

• Aim:

Providing students with a chance of explaining the metallic bonding with their own words.

To assess students’ level of understanding within the lesson.

• At the end of the first lecture, teacher asks students to define the similarities between metallic bonding and this activity.

Analogy (Baloon Activity)

• Teacher asks:

“How can we make connection between metallic bonding and baloon activity in the light of things that we learned?”

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.

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?”

2ND LECTURE

HOUR( 45 min.)

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INITIATION ( 5 min)

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.

MAIN BODY ( 30 min.)

Malleability• 03.42 – 05.10 ( Metallic Bonding

youtube) garip konusan adam

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)

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.

Malleability

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.”

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

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?”

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.

Thermal Conductivity Experiment

• Activity will be done by grouping students. Each group will consist of 3-4 students.

• Video of the experiment

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.”

Metallic lustre

Metallic Lustre

• Teacher ask:

“How can metals look like so shiny?”

Expectation: We don’t expect students to give the detailed answer, but they may state that

Metals reflect the light

Metallic Lustre

• “ Valence electrons in the sea of electrons are free to wander throughout the material with little resistance.”

• “ When light shines on metal, it sets these free electron into vibration.”

Metallic Lustre

• Instead of energy springing from atom to atom, it is reemitted as visible light.

CLOSURE( 10 min.)

Assesment within Class

• Teacher gives a worksheet containing multiple choice and true/false questions to students to assess students’ understanding of metallic bonding

• Worksheet

OTHER ASSESMENT

Assessment

• Teacher asks 2 open ended questions as homework. Due date is next lesson.

What can be the reason of different rates of thermal conductivity of different metals?

Do you think that all metals shine in the same amount? Explain.

REFERENCES• http://download.springer.com/static/pdf/808/art%25

3A10.1007%252Fs11165-007-9054-9.pdf?auth66=1352729340_32473fe26c4b1dfeb48e4ff8a833841a&ext=.pdf

• http://www.cedarville.edu/personal/lee/project/demos/demo-sim-metallic-bond.pdf

• http://www.youtube.com/watch?v=Bjf9gMDP47s

• http://www.youtube.com/watch?v=DbKECtWNm8k

• http://www.yteach.com/

• http://www.youtube.com/watch?v=xTx_DWboEVs

• http://www.youtube.com/watch?v=lcXMIzprd14