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?
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
2 bonding domains Three bonding domains Four bonding domains Three bonding and one lone pair Two bonding and two lone pairs
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)
A polar molecule has polar bonds and asymmetry Polar bonds Non-polar molecule Symmetry- all sides are the same δ - δ - δ - δ - δ +
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
If the electrons are not distributed equally, the molecule is polar. The molecule has a negative end and a positive end.
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
Polar molecules are affected by electric fields
Polar molecules have two poles; one is partially positive and one is slightly negative. Positive end Negative end N H H H
The positive pole ( + ) is attracted to negative ions and the negative poles( - ) in other polar molecules. POLAR MOLECULES INTERACT!!
+ POLAR MOLECULES INTERACT!! The negative pole ( - ) is attracted to positive ions and the positive poles( + ) in other polar molecules.
Water is a molecule that has two polar O-H bonds.
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
Water is very good at dissolving salts because it can surround anions & cations.
Practice- Using last night’s homework assignment, label the molecular polarity on the four pictures H F
<ul><li>For the rest of the period work on your molecular modeling lab </li></ul><ul><li>Find a molecule that contains polar bonds </li></ul><ul><li>Build the molecule using a molecular modeling kit </li></ul><ul><li>Draw a sketch of the molecule </li></ul><ul><ul><li>Label the bond polarity using δ + and δ - </li></ul></ul><ul><ul><li>Label the molecular polarity using </li></ul></ul>HW- complete bonding practice problems #1-#17 Tuesday = cover network solids and intermolecular forces. HW- Section 8.4 Block Day = Complete modeling lab, plus finish bonding practice problems. Friday = Chapter Eight QUIZ!!
Practice- Draw the 3D structures for these molecules and label the bond polarity and the molecule polarity. <ul><li>H 2 O </li></ul><ul><li>CH 4 </li></ul><ul><li>CH 3 F </li></ul><ul><li>CH 3 CH 3 </li></ul><ul><li>CH 3 CH 2 OH </li></ul><ul><li>6. NH 3 </li></ul>7. CO 2 8. CH 2 CH 2 9. HCN 10. 11.