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Objectives:

Objectives:. To use electronegativity and the location of elements on the periodic table to predict the type of bond (polar, nonpolar, ionic) To describe dispersion forces, dipole-dipole interaction, and hydrogen bonding. Drill:.

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Objectives:

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  1. Objectives: • To use electronegativity and the location of elements on the periodic table to predict the type of bond (polar, nonpolar, ionic) • To describe dispersion forces, dipole-dipole interaction, and hydrogen bonding

  2. Drill: • Give all the combinations of the number of bonded pairs and nonbonded pairs of electrons for a bent structure.

  3. Homework • Complete Worksheet • Read lab and complete pre-lab questions

  4. Intramolecular Forces The forces of attraction that exist between bonds within a molecule.

  5. Dipole • Charged ends of a molecule • Represented by δ+ or δ- • Slightly positive - δ+ • Slightly negative - δ-

  6. Nonpolar Bond • When two atoms have the same electronegativity. • No dipole is formed

  7. Polar Bond • When the electronegativities of the atoms differ. • The greater the difference the more polar the bond • A dipole may form

  8. Ionic Bonds • Atoms on opposite sides of the table have large differences in electronegativity. • Bonds are highly polar • ΔEN > 1.8

  9. Nonpolar Covalent Bonds • Nonmetallic atoms of the same type have the same electronegativity • Bonds are nonpolar • ΔEN < 0.4

  10. Polar Covalent Bonds • Atoms in between these two extremes have an uneven sharing of electrons • Slightly charged atoms • 1.8 ≥ ΔEN ≥ 0.4

  11. Intermolecular Forces • The attraction between molecules • The stronger the intermolecular forces the more energy it takes to change phases

  12. Types of Intermolecular Forces • Ion • Charged particle • Dipole • Polar molecule • Induced dipole • Non-polar molecule induced into having a temporary dipole

  13. Types of Intermolecular Forces • Strengths of intermolecular forces • Ion – ion (strongest) • Ion – dipole • Dipole - dipole • Dipole – induced dipole • Induced dipole – induced dipole (weakest)

  14. Very special intermolecular force • Hydrogen bonding • An unusually strong dipole-dipole attraction • Between molecules with a hydrogen atom attached to a very electronegative atom • (F or O or N or . . .)

  15. Summary of Types of Intermolecular Forces

  16. Molecular Polarity • Non Polar Molecule • All bonds in the molecule are nonpolar • Dipoles of equal strength but pull in opposite directions, cancel each other out. The net result is an even distribution of bonding electrons around the whole molecules • Often symmetrical in shape

  17. Molecular Polarity • Polar Molecule • There is an uneven distribution of bonding electrons. • Often asymmetrical in shape

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