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Electronegativity & Polarity

Electronegativity & Polarity. What makes polar covalent bonds? Unequal sharing of the electrons. What makes non polar covalent bonds? Equal sharing of electrons. . Difference in electronegativities is a rough measure of the character of bonding between two elements. The

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Electronegativity & Polarity

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  1. Electronegativity & Polarity

  2. What makes polar covalent bonds? Unequal sharing of the electrons. • What makes non polar covalent bonds? Equal sharing of electrons.

  3. Difference in electronegativities is a rough measure of the character of bonding between two elements. The electronegativity of the less electronegative element is subtracted from that of the more- electronegative element. The greater the electronegativity difference is, the more ionic the bonding is.

  4. Practice ProblemsPage 26660-63

  5. Partially Partially Positive negative • Dipole-dipole forces

  6. HCl is Polar

  7. Water (H2O) is Polar!

  8. VSEPR Valence Shell Electron Pair Repulsion The shape of H2O determined by VSEPR is bent because there are two lone pairs of electrons on the centraloxygen atom.

  9. Ammonia (NH3) is Polar • Anytime you have extra PAIRS of electrons on one side of the molecule it is POLAR

  10. BrF5 is Slightly polar Unshared pair

  11. Chloromethane •• •• •• Polar or non polar?

  12. Methane Polar or non polar?

  13. NON POLAR MOLECULES The shape of CCl4 is tetrahedral and the molecule is symmetric. The electrical charge measured at any distance from its center is identical to the charge measured at the same distance on the opposite side.

  14. Non Polar Molecules CO2

  15. CO3 –2

  16. SiBr4

  17. Which molecules are Polar?

  18. Intermolecular Forces Weakest to strongest: 1. dispersion forces, aka London dispersion 2. dipole-dipole 3. Hydrogen bonding is a type of dipole-dipole force, but is the force between hydrogen end of one dipole and a fluorine, oxygen or nitrogen atom on another dipole.

  19. 1. London dispersion Forces • Weakest intermolecular force. • Temporary between adjacent atoms Due to constant motion of the electrons, an atom or molecule can develop a temporary (instantaneous) dipole when its electrons are distributed unsymmetrically about the nucleus.

  20. 2. Dipole-dipole intermolecular force • Chlorine is in period 3 and is a fatter atom than O or F. • Other examples: H & Br, H & I even fatter atoms Connected 1 dipole 1 dipole Dipole-dipole intermolecular force

  21. 3. Hydrogen Bonding Hydrogen bonding is between very small, very electronegative atoms H & N, H & O H & F Note: N, O, & F are all in Period 2 (only 2 energy levels) Electronegativity increases up family & across period

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