Bell Work: • Draw and name the structure of Sulfur Dioxide.
8.4 Bond Polarity • The bonding pairs of electrons in covalent bonds are pulled by the nuclei.
8.4 Bond Polarity • Chlorine is more electronegative than Hydrogen so it attracts the electron cloud more than the hydrogen atom does.
8.4 Polar Molecules • In a polar molecule, electrons are not shared equally. One end of the molecule (the more electronegative) has a stronger pull and is slightly negative and the other end is slightly positive • A molecule that has two poles is called a dipolar molecule, or dipole.
Polar or Non-Polar? • a) O2 • b) HCl • c) H2O • d) CO2
Polar bond vs Polar molecule • Sometimes a bond is polar but the molecule is non polar!!
8.4 Bond Polarity Bottom Line: The higher the electronegativity difference, the more polar the molecule!!
Warm Up • Draw the structure for BH3 and determine its polarity.
8.4 Attractions Between Molecules • (2 types of intermolecular attractions = very weak) • Van der Waals Forces • Dipole Interactions: when polar molecules are attracted to one another. • Dispersion Forces: Caused by the motion of electrons. Creates temporary Dipoles.
8.4 Attractions Between Molecules • Dispersion forces, the weakest of all molecular interactions, are caused by the motion of electrons. • The strength of dispersion forces generally increases as the number of electrons in a molecule increases.
8.4 Attractions Between Molecules • 2) Hydrogen Bonds • Hydrogen bonds are attractive forces in which a hydrogen covalently bonded to a very electronegative atom is also weakly bonded to an unshared electron pair of another electronegative atom.
8.4 Attractions Between Molecules • Hydrogen Bonding in Water
8.4 Attractions Between Molecules • The relatively strong attractive forces between water molecules cause the water to form small drops on a waxy surface.
8.4 Section Quiz. • 8.4.
8.4 Section Quiz. • 1. In a molecule, the atom with the largest electronegativity value • repels electrons more strongly and aquires a slightly negative charge. • repels electrons more strongly and aquires a slightly positive charge. • attracts electrons more strongly and aquires a slightly positive charge. • attracts electrons more strongly and aquires a slightly negative charge.
8.4 Section Quiz. • 2. When polar molecules are placed between oppositely charged plates, the negative • molecules stick to the positive plates. • molecules stick to the negative plates. • ends of the molecules turn toward the positive plates. • ends of the molecules turn toward the negative plates.
8.4 Section Quiz. • 3. Which of the following bond types is the weakest? • ionic bond • Van der Waals force • covalent bond • hydrogen bond
Chem ASAP • Concept Map 8 Solve the Concept Map with the help of an interactive guided tutorial.