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Understanding Covalent Bonds: Types, Shapes, and Polarity

Learn about covalent bonds, diatomic molecules, bond types, molecular shapes, and polarity. Discover how to determine bond type, shape, and polarity of molecules, and practice naming molecules and predicting states of matter. Test your knowledge with a chapter review quiz.

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Understanding Covalent Bonds: Types, Shapes, and Polarity

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  1. Chapter 9: Covalent Bonds

  2. Visual Preview • Video Link • Unavailable online • Internet Link • (http://www.visionlearning.com/library/module_viewer.php?mid=55&l=&c3=)

  3. What is a Covalent Bond? • Covalent Bond -The result of sharing valence electrons. The shared electrons are part of the complete outer shell of both atoms. • Occurs when elements are close together on the periodic table • Between nonmetallic elements • Molecule-formed when two or more atoms bond covalently.

  4. Covalent Bonds • Can exist as gases, liquids, or solids depending on molecular mass or polarity • Usually have lower MP and BP than ionic compounds • Do not usually dissolve in water • Do not conduct electricity

  5. Types of Bonds: • Nonpolar covalent (also called pure covalent) – equal sharing of electrons between atoms; example: O2 • Polar covalent – unequal sharing of electrons between atoms; example: H2O • Ionic – complete transfer of electrons; example: NaCl • *electronegativity (EN) – indicates how strongly an atom wants to gain an electron

  6. Diatomic Molecules • Contains only two atoms. 7 naturally occurring in nature • H H2 • O O2 • F F2 • Br Br2 • I I2 • N N2 • Cl Cl2

  7. TO PREDICT BOND TYPE: • Look at table of EN values and subtract the values for the 2 atoms involved in the bond • take the absolute value • If EN difference is… • 0 – 0.4 nonpolar covalent bond • 0.5 – 1.6 polar covalent bond • >1.7 ionic bond

  8. TO DETERMINE MOLECULAR SHAPE • Use VSEPR (valence shell electron pair repulsion) rules: 1) Draw the Lewis dot structure for the molecule 2) Identify the central atom 3) Count total # of electron pairs around the central atom 4) Count # of bonding pairs of electrons around the central atom 5) Count # of lone pairs of electrons around the central atom 6) Look at summary chart, identify shape

  9. Practice: • Determine the shape.1. BCl32. CaO

  10. Polarity • TO DETERMINE THE POLARITY OF A MOLECULE,not a bond, you must know the type of bond and the shape. • POLAR MOLECULES must meet 2 criteria: • Must have a polar covalent bond (EN difference between 0.5 and 1.6) AND

  11. Determining Polarity • Must have an asymmetrical shape: • trigonal pyramidal or • angular, or • 2 element linear • If both criteria are not met, it is not a polar molecule, it is either a nonpolar molecule or an ionic compound.

  12. Practice: • Label the following MOLECULES as polar or nonpolar. • 1. NH3 • 2. CH4 • 3. HCl

  13. Practice: • What type of bond that will occur between each of the following? • 1. BCl3 • 2. CaO

  14. Lewis Structures for Molecules • Single Covalent Bonds • Hyrdrogen + Bromine • Carbon + Chlorine

  15. Naming Molecules • Binary molecules-Rules • Name the first element using the entire name • The second element is named using the root and the suffix (ending) –ide • Prefixes are used to indicate the number of each type of atom. (Table 9-1) Exception-the first element will never have the prefixmono

  16. TO DETERMINE STATE OF MATTER: 1. Determine if compound is ionic, polar, or nonpolar. 2. Calculate molar mass of compound by adding the mass of each of the elements in the compound. 3. Look at the state of matter chart.

  17. Practice: • What is the state of matter of the following compounds? 1. HBr 2. NH3 3. CaCl2

  18. Chapter Review Quiz • Take the online review quiz from the textbook to get an idea of how you might perform on the multiple choice portion of the test. • If you scored less than 14 of 20 correct 70% you need to spend more time studying.

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