Section 8.4 lecture (part B) for Honors & Prep Chemistry

1. BELLWORK- Determine Shape Draw the Lewis Dot Structure and the 3D structure for ethane (C 2 H 6 ) and ethene (C 2 H 4 ). Do these molecules have any polar bonds?

2. In review Equal sharing of electrons = covalent LOW electronegativity difference Unequal sharing of electrons = polar MEDIUM electronegativity difference Transfer of electrons = ionic HIGH electronegativity difference

3. 2 bonding domains Three bonding domains Four bonding domains Three bonding and one lone pair Two bonding and two lone pairs

4. Bond polarity and molecule shape determine if a molecule is polar Bond polarity --- When a bond has a partial negative charge on one atom and a partial positive charge on the other atom. Molecule shape--- the arrangement of atoms in three dimensions (3-D)

5. A polar molecule has polar bonds and asymmetry

6. A polar molecule has polar bonds and asymmetry Polar bonds Non-polar molecule Symmetry- all sides are the same δ - δ - δ - δ - δ +

7. A polar molecule has polar bonds and asymmetry Polar bonds Non-polar molecule Symmetry- all sides are the same Polar bonds Polar molecule Asymmetry- has different sides δ - δ - δ - δ - δ - δ + δ + negative side Positive side

8. If the electrons are not distributed equally, the molecule is polar. The molecule has a negative end and a positive end.

9. A polar molecule has a partially positive side and a partially negative side. The arrow labels the molecular polarity. It shows that electrons are mostly by the oxygen atom O H H

10. Polar molecules are affected by electric fields

11. Polar molecules have two poles; one is partially positive and one is slightly negative. Positive end Negative end N H H H

12. The positive pole (  + ) is attracted to negative ions and the negative poles(  - ) in other polar molecules. POLAR MOLECULES INTERACT!!

13. + POLAR MOLECULES INTERACT!! The negative pole (  - ) is attracted to positive ions and the positive poles(  + ) in other polar molecules.

14. Water is a molecule that has two polar O-H bonds.

15. The electrons are not distributed evenly, so the water molecule is polar. The negative pole is at the oxygen. O is more electronegative than H, so electrons are pulled toward O. Also, there are two lone pairs around oxygen. negative end positive end

16. Na + (aq) A dissolved sodium ion

17. Water is very good at dissolving salts because it can surround anions & cations.

18. Practice- Using last night’s homework assignment, label the molecular polarity on the four pictures H F