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Understanding Covalent Bonding Through Electron Sharing and Lewis Dot Diagrams

In this engaging lesson, students will explore the concept of covalent bonding by demonstrating the sharing of electrons through Lewis dot diagrams. We will cover the characteristics that distinguish covalent bonds from ionic and metallic bonds, and examine examples using various compounds. The lesson will include multimedia resources, interactive webquests, and a hands-on laboratory component focusing on chromatography. Students will learn how to predict bond types based on electronegativity, and will summarize their understanding through a quiz and exit ticket.

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Understanding Covalent Bonding Through Electron Sharing and Lewis Dot Diagrams

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  1. Drill: • Ionic bonding • Objective: • Swbat: Demonstrate sharing of electrons in order to model covalent bonding by combining Lewis dot diagrams.

  2. SAT ENRICHMENT: • The bonds in BaO are best described as…. • Covalent, because valence electrons are shared. • Covalent, because valence electrons are transferred. • Ionic, because valence electrons are shared. • Ionic, because valence electrons are transferred. • Metallic, because valence electrons exist in a “mobile sea”.

  3. ENGAGEMENT: • Safari Montage Video: Properties of Compounds: Covalent Bonding: http://10.4.1.240/?p=d9e9fc51-8f49-11df-8b67-002219bf32de

  4. Covalent Bonding WebQuest! • Covalent Bonding Webquest (SR.CHEMBOND.02A) • http://www.visionlearning.com/library/module_viewer.php?mid=55&mcid=&l= 30 min

  5. Covalent Compounds • Covalent Bonds • Two nonmetals • Weaker than ionic bonds • Electrons shared, not transferred

  6. Covalent Compounds • Example: Chlorine and fluorine (ClF) • Problem 1: Sulfur and oxygen (SO) • • • • ◙ ◙ ◙ ◙ • • → • • Cl + F ◙ Cl F ◙ • • ◙ ◙ ◙ ◙ • • • • ◙ ◙ ◙ ◙ • • • • ◙ • • → • • O ◙ S + O ◙ S ◙ • • • ◙ ◙ ◙ ◙ • ◙ ◙ ◙ ◙

  7. Covalent Compounds • Problem 2: Selenium and bromine (SeBr2) • Problem 3: Carbon and oxygen (CO) • • • • • ◙ ◙ ◙ ◙ • • • • → Br Se Br Se Br + + ◙ ◙ ◙ ◙ • • • • • • ◙ ◙ • • • • • • • ◙ ◙ • • Br • • • • • ◙ ◙ • → • C + ◙ O ◙ C ◙ ◙ O ◙ • • • • ◙ ◙ ◙ ◙ • ◙

  8. Bond Polarity If there is an unequal sharing of electrons, the bonding electrons spend more time near the atom with the highest electronegativity causing it to obtain a slightly negative charge. The atom with the lower electronegativity acquires a slightly positive charge.

  9. Electronegativities • Electronegativities for the first six periods • The difference between two elements’ electronegativities indicates the degree of electron sharing (or transfer) in a chemical bond • The closer the electronegativity, the more equally the electrons are shared.

  10. Polar or Nonpolar? Nonpolar Covalent Bond- • Electronegativity difference ≤ 0.4 Polar Covalent Bond • 0.4 < Electronegativity difference < 1.7

  11. Predicting Bond Type Example 1: OF2 • EN of O = 3.5 • EN of F = 4.0 • 4.0 – 3.5 = 0.5 0.5 is less than 1.7 but greater than 0.4, so the bond is polar covalent.

  12. Predicting Bond Type • Example 2: Cl2 • EN of Cl = 3.0 • 3.0 – 3.0 = 0.0 • 0 ≤ 0.4, so the bond is nonpolar covalent.

  13. Predicting Bond Type Example 3: CS2 C: 2.5 S: 2.5 2.5 – 2.5 = 0.0 Nonpolar Covalent

  14. Predicting Bond Type Example 4: NH3 N: 3.0 H: 2.1 3.0 – 2.1 = 0.9 Polar Covalent

  15. Special Case: Polar Covalent • Polar covalent molecules have a dipole • Molecules with dipoles have partially charged ends • For water: • Oxygen has an electronegativity of 3.5 • Hydrogen has an electronegativity of 2.1 • Because oxygen is more electronegative, it will be the negative end of the dipole • Because hydrogen is less electronegative, it will be the positive end of the dipole ◙ ◙ O H ◙ ◙ • Negative ◙ • ◙ H Positive

  16. Bonding • Complete bonding worksheet 10 min

  17. Summary: • Did we accomplish the objective? Explain. • Define a Covalent bond. • What criteria would you use to assess whether a bond is ionic or covalent? • What criteria would you use to assess whether a bond is polar or nonpolar?

  18. Homework: • Chromatography Pre-Lab • (NO HOMEWORK PASSES MAY BE USED)

  19. Drill: • Quiz: Covalent Bonding (5 min) • Objective: • Swbat: Demonstrate sharing of electrons in order to model covalent bonding by combining Lewis dot diagrams.

  20. SAT ENRICHMENT: • Generally… valence electrons are needed for atoms to be most stable. • 2 • 6 • 8 • 18 • 32

  21. Chromatography Lab • Review Lab procedures. • Chromatography Lab 45 min

  22. Exit Ticket & Extension • Covalent Bonding Exit ticket • Extension: Oil and Soap Molecule Simulation: http://intro.bio.umb.edu/111-112/111F98Lect/soapandoil.html 5 min

  23. Summary • Did we accomplish the objective? Explain. • Identify the purpose of the chromatography lab. • Explain your chromatography lab results. Which colors were soluble in water?

  24. Homework • Instructional Fair Pages 38 and 39!

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