Going with the Trends:Going with the Trends:PERIODIC TRENDSPERIODIC TRENDS

Concept PresentationConcept PresentationAndrew Selvam – HS Chemistry OISE/UTAndrew Selvam – HS Chemistry OISE/UT

Instructors: Janine Extavour/Marty ZatzmanInstructors: Janine Extavour/Marty Zatzman

Outline of Presentation

• Curriculum Expectations• What do I need to know before?• Where does the concept fit?• Roadblocks and Misconceptions for Teachers and Students

(incl. Solutions and Activities) • Lesson Sequence (incl. Accommodations and A&E)• Applications to Real World• Period Trends War Game• References

Curriculum Expectations(Ontario Ministry of Education)

SPECIFIC EXPECTATIONS

Curriculum Expectations(Ontario Ministry of Education)

Review Items

• Grade 9 and 10 Science– The Atom

• Composition of the Atom

• Subatomic Particle

– Formation of Ions

– Periodic Table• Elements

• Features – Atomic Number and Atomic Mass

• Periods (Rows) and Groups (Columns)

of elements with similar properties

F

F F1-

The Unit

• Periodic Trends is part of the first unit of SCH 3U• Integral for students to understand the molecular/atomic

basis for the formation of compounds and the reaction of those compounds (later in the unit)

Chapter 1 Observing

Matter

Chapter 2Elements and the Periodic

Table

Chapter 3Chemical

Compounds and Bonding

Chapter 4Classifying Reactions:

Chemicals in Balance

Placement of Concept in the Chapter

• The placement of the concept of the unit fits appropriately in the context of the chapter

• Both McGraw-Hill and Nelson texts place the concept in the following way:

Atoms, Elements and the Periodic Table

Periodic Trends(Involving the Sizes

and Energy Levels of Atoms)

Classifying Chemical Compounds

(Ionic vs. Covalent)

Why do you think this is?

The Concept

PERIODIC TRENDSPERIODIC TRENDS

Atomic RadiusAtomic Radius

Ionization EnergyIonization Energy

Electron AffinityElectron Affinity

ElectronegativityElectronegativity

ReactivityReactivity

Effective Nuclear Charge

Effective Nuclear Charge

Shielding EffectShielding Effect

The Trends in Picture

Major Roadblocks for Teachers

Teachers have a two-fold problem when it comes to teaching periodic trends:1. Explaining (as opposed to simply memorizing) the subatomic basis

for all five trends• Atomic Radius (Ionic Radius)

• Ionization Energy

• Electron Affinity

• Electronegativity

• Reactivity of Metals and Non-Metals

2. Looking for ways to help students retain

and review the knowledge of Periodic Trends

Misconceptions for Students

ROADBLOCK #1• Visualizing attractive and repulsive forces between nucleus

and electrons

ROADBLOCK #2• Understanding that the nucleus can have an ‘effective nuclear

charge’ and that inner-level electrons can shield the nucleus from outer-level electrons

Ryan Seacrest shows Effective Nuclear Charge with his smile!

The Solution to Misconceptions 1 and 2:

The Analogy with Atomic Radius

• Ryan Seacrest = Nucleus

• Mouthwash = Effective Nuclear Charge

• Ladies = Electrons

Using Desks in Your Classroom

Teacher’s Desk = Nucleus = Electron

ROADBLOCK #3Each periodic trend is really its own separate concept. None of them are interconnected.

Visual: Across a Period…H

Li Be

Na Mg

Na

11P12N

Mg

12P12N

ATOMIC RADIUS- Adding one proton increases the charge of the nucleus to pull the electrons towards them, therefore across a period, the atomic size decreases

Na

11P12N

Mg

12P12N

IONIZATION ENERGY- It requires more energy to pull electrons that have been tightly held by the nucleus, therefore across a period, the ionization energy increases

ELECTRON AFFINITY/ ELECTRONEGATIVITY- Because the electrons are being tightly held by the nucleus, therefore across a period, electron affinity and electronegativity increases.

Visual: Down a Group…H

Li Be

MgNa

Li

3P4N

Na

11P12N

Li

3P4N

Na

11P12N

ATOMIC RADIUS- Going down a period, there are additional energy levels to add to the size of the atom, thus the atomic radius increases

IONIZATION ENERGY-It requires less energy to pull electrons that are not tightly held by the nucleus, therefore down a group, the ionization energy decreases

ELECTRON AFFINITY/ ELECTRONEGATIVITY- The electrons are not being as tightly held by the nucleus, therefore across a period, electron affinity and electronegativity decreases.

Each of you will receive two magnets:

Here are your instructions:• Take a few minutes in pairs or in table groups to come up

with a way to use the magnets to explain a periodic trend

Now here is how you can use magnets to

show some of the periodic trends...

Using Magnets for Ionization Energy

• Take two magnets. The first magnet is the nucleus and the second magnet are the electrons in the outer shell.

• When the magnets are close together – hard to pull them away from each other – requires more energy

• When the magnets are already far apart, – it is easy to pull them further away, because of a weak force of

attraction

Lesson Day 1Focus: Review of Atomic Composition and Atomic Structure

Activities: - Chalk and Talk on Composition/Structure

- Demo 1: Atomic Emission Spectra

(Use Diffraction Gratings and Spectroscopes)

- Demo 2: Metal Reactivity (With Alkali Metals)

- Will Refer Back to Later in the Lesson Sequence

Accomodations: For IEP/ELL students, provide them with tables that give them an idea of how the number of valence electrons relate to groups on the periodic table

Assessment/Evaluation: Assessment for Grade 9 Review Items

Formative Assessment – Metal Reactivity Demo

Homework – Effective Nuclear Charge

Demo: Observing the Spectra of Elements

H2 D2 N2 O2 Hg

He Ne Ar Kr Xe

Demo: Metal Reactivity

Li

Na K

Metal Reactivity increases as you move down the

group.

Safety Precautions for Demo

• Lab not recommended for students as it can be quite violent

• Metals like lithium, potassium, and sodium react violently with air and so are kept in a special mineral oil

• If you have a shield, put this up to prevent injury or ask students to move back

Lesson Day 2Focus: Introduction to Periodic Trends

Activities: - PowerPoint on Periodic Trends including Analogies

- VAK Activities:

- Magnet Analogy (Visual)

- Classroom Kinesthetic Activity

- Trends Exercise (Aural)

(Students can pair together to try activities)

- Discussion on Applications to the Real World

Assessment/Evaluation: Diagnostic Questioning – Previous Day Learning

Formative Assessment – Worksheet/Text Ques.

Formative Assessment – Exit Pass

Multiple Intelligences: Visual, Logical, Tactile, Interpersonal, Intrapersonal

Lesson Day 3Focus: Reinforcement of Periodic Trends

Activities: - Periodic Trends War Game (We will do this at the end!)

- Graphical Analysis of Periodic Trends

- Atomic Radius vs. Atomic Number

- Ionization Energy vs. Atomic Number

Assessment/Evaluation: Formative Assessment –

- Taking in Game Sheet for Periodic Trends War

- Taking in Graphs to get proof of student understanding

- Teacher will go around to help students one-on-one with activity

Multiple Intelligences: Visual, Logical, Intrapersonal, Interpersonal

Graphic Resource for Periodic Trends<http://www.teachersdomain.org/resource/lsps07.sci.phys.matter.graphperiodic/>

Assessment & Evaluation:KICA

Knowledge Questions that ask to find the element with the greatest or least atomic radius, ionization energy

Inquiry Questions that ask students to explain the atomic basis for periodic trends

Communication Graphical analysis of periodic trends

Application Discussion on uses of elements based on their place in the Periodic Table

Applications to the Real World

• Medical (Surgical)– Because of the low reactivity

of Tantalum (Ta) [bottom-left] of the PT, used in surgical sutures, pins, and implants

• Cooking– Because fluorine is so

reactive it reacts with another substance, and becomes very stable. Teflon used in pans is a combination of carbon and fluorine.

More Applications...

• Industrial– Tantalum oxide is used in

camera lenses

– Cesium (Cs) has a low ionization energy and is very reactive

– It is used in TV cameras and traffic signals

– Chlorine and bromine are used for sterilization (high reactivity)

Periodic Trends War

• This is an adaptation of the card game ‘war’, except instead of using playing cards, we will use index cards with an element on it

• We will also use dice, where each face represents one of the trends:

• 1 – Atomic Radius/Ionic Radius

• 2 – Ionization Energy

• 3 – Electron Affinity

• 4 – Electronegativity

• 5 – Reactivity

• 6 – ‘Wild’ – Any of the trends above

Periodic Trend War Cont’d

Instructions:

1. Students get into groups of 3 or 4. Assign someone to be the dealer.

2. The dealer will roll the die. Each student in the group will reveal the element card from the top of their pile

3. It is now up to them to determine who wins the deal based on who has the greatest value based on the trend

4. The person who wins becomes the dealer

Activity Assessment and Evaluation

• Each student will get a game card• The student will document the name of the trend, the

choices they had and the atom with the greatest value• At the end of class, students will hand the game card in as a

formative assessment• The teacher now has a better understanding of whether the

student knows the trend

Potential Advantage: Peer Collaboration

Potential Disadvantage: Peer Plagarizing

Text References

McGraw-Hill Chemistry 11• Student Text and Teacher’s Resource

Addison-Wesley Chemistry 11•Teacher’s Resource

Provides Suggestions for:• Common Student Misconceptions• Lesson Ideas for all Learning Styles• Accommodations for Identified / ELL Learners• Assessment and Evaluation• Possible Lab Investigations

Montogomery, M. (2005). Periodic Table Trends. The Science Teacher, 72(4), 50-51.

• This resource comes from a science teacher at a local highschool in Southaven, Mississippi. The author attempts to provide examples of how to demonstrate the trends of atomic radius, ionic radius, and ionization energy by reorganizing the desks in a classroom. He also tackles concepts such as the shielding effect.

• Also goes into great explanations for ionic radii as well

Journal Articles

Websites

Website: Howe, M., Krone, B., Reiter, S., and D. Verby.

Chemistry as Fun and Games.

<http://nobel.scas.bcit.ca/chemed2005/tradingPost/TUPM_S2_4_15ChemFunGames.pdf.>

• Good resource for games that apply to concepts learned in Grade 11 and 12 Chemistry

YouTube Videos – Periodic Trends Song

<http://www.youtube.com/watch?v=MGTKVaZcq8Y>• Cheesy song for students who might enjoy learning in the musical

genres of hip-hop and rap

Don't forget me!Thanks for listening to

my presentation!And thanks to Cora for all

her support!

If you ever thought periodic trends could not be cool, wait until

you listen to this cheesy music video...