VSEPR Theory and Molecular Shapes Lab

Make sense of problem and persevere in solving them Objective Today I will be able to: Draw Lewis Structures to represent the valance electrons of atoms Represent the formation of ionic and covalent compounds using Lewis Structures Predict the molecular shape of a molecule using the VSEPR theory Evaluation/ Assessment Informal assessment – Listening to group interactions as they complete the illustrating ionic and covalent compounds practice and the molecular shapes lab. Formal Assessment – Analyzing student responses to the exit ticket and the practice worksheets. Common Core Connection Make sense of problem and persevere in solving them Reason abstractly and quantitatively Use appropriate tools strategically Look for and make use of structure

Lesson Sequence Warm – Up Explain: Writing an Abstract Explain: VSEPR Theory (Day 1) Explore and elaborate: Molecular Shapes Lab (Day 1 & 2) Informal Assessment Evaluate: Exit Ticket Formal assessment

Warm - Up How do I determine the number of valence electrons an atom has? How many valence electrons does the following elements have: 1) Boron 2) Nitrogen 3)Barium

Objective Today I will be able to: Draw Lewis Structures to represent the valence electrons of atoms Represent the formation of ionic and covalent compounds using Lewis Structures Predict the molecular shape of a molecule using the VSEPR theory

Homework STEM Fair Conclusion Re-Dos due Monday the 15th Abstract due Friday Dec 19th

Agenda Warm-Up Writing an Abstract VSEPR Notes (Day 1) Molecular Shapes Lab (Day 1 & 2) Exit Ticket

Writing an Abstract

What is an abstract? A concise summary of your experiment Summarized in 250 words or less STEM Fair judges will read over your abstract to understand what you did in your project

Components of an Abstract Problem Statement and hypothesis Brief explanation of experimental procedure A brief overview of results With quantitative data included Conclusion Application and (or) relevance of findings Write in past tense and passive voice

Example # 1 This project will exdplain whether or not antibacterial soap really kill germs. Antibacterial soap is known to be the most germ killing soap. To perform this experiment you must have a veriable and a control. The variable will be the antibacterial soap in which you will have to test three differnt times for each of the 3 soaps. The soaps will be Daial with antibacterial and dial without antibacterial, lever2000 with antibacterial and Lever without antibacterial, zest with antibactrial and zest without antibacterial. The control will be regular soap. The test will be used using petri dishes with chicken broth in them. Chicken broth makes it easier to see germs.

Example # 2 Advertisers are always touting more powerful and longer lasting batteries, but which batteries really do last longer, and is battery life impacted by the speed of the current drain? This project looks at which AA battery maintains its voltage for the longest period of time in low, medium, and high current drain devices. The batteries were tested in a CD player (low drain device), a flashlight (medium drain device), and a camera flash (high drain device) by measuring the battery voltage (dependent variable) at different time intervals (independent variable) for each of the battery types in each of the devices. The hypothesis was that Energizer would last the longest in all of the devices tested. The experimental results supported the original hypothesis by showing that the Energizer performs with increasing superiority, the higher the current drain of the device. The experiment also showed that the heavy-duty non-alkaline batteries do not maintain their voltage as long as either alkaline battery at any level of current drain.

STEM Fair Dates December 15th: Conclusion Re-Dos December 19th: Abstract December 22nd: Abstracts Returned Re-Dos are due through email to Mr. Klotz david_klotz@hcpss.org January 9th: In-Class Presentations January 29th: Howard HS STEM Fair Tell them we will discuss board stuff on the Monday before winter break

Drawing Lewis Structures

Lewis Structures Visual representation of the number of valence electrons in an atom

How to draw Lewis structures Write the symbol of the element Pretend there are 4 sides Use dots to represent the valence electrons around the symbol Place one dot on each side of the element before you form pairs Exception: If there are only 2 valence electrons, they both go on the same side

Lewis Structures C 1s2 2s2 2p2 • • • C •

Lewis Structures Examples Mg 1s2 2s2 2p6 3s2 • Mg •

Lewis Structures Cl 1s2 2s2 2p6 3s2 3p5 • • • • Cl • • •

[ ] • • • • • • • • Cl -1 Lewis Structures Cl 1s2 2s2 2p6 3s2 3p5

VSEPR Theory Notes

Valence – Shell Electron Pair Repulsion Theory (VSEPR) In a small molecule, the pairs of valence electrons are arranged as far apart from each other as possible Explains why atoms form certain shapes when they bond together

Linear Bonds Formed: 2 Lone Pairs: 0 Bond Angle: 180o

Trigonal Planar Bonds Formed: 3 Lone Pairs: 0 Bond Angle: 120o

Tetrahedral Bonds Formed: 4 Lone Pairs: 0 Bond Angle: 109.5o

Trigonal Pyramidal Bonds Formed: 3 Lone Pairs: 1 Bond Angle: <109.5o

Bent (Tetrahedral) Bonds formed: 2 Lone Pairs: 2 Bond Angle: <109.5o

Bent (Trigonal Planar) Bonds Formed: 2 Lone Pairs: 1 Bond Angle: <120o

Trigonal Bipyramidal Bonds Formed:5 Lone Pairs: 0 Bond Angle: 120o and 90o

Octahedral Bonds formed:6 Lone Pairs: 0 Bond Angle: 900

Molecular Shapes Lab

Molecular Shapes Lab Directions Draw a Lewis Dot Structure for the molecule Make a model using the kit and draw the shape on your paper Write the shape name Write the bond angle Skip POLARITY for now, and we will come back to this part Be careful with the kits, do not drop or lose pieces!

Exit Ticket Draw the Lewis Structure for CO2 Determine the shape and bond angles of CO2 according to the VSEPR theory.