Chapter 8 Covalent Bonding 8.4 Polar Bonds and Molecules 8.1 Molecular Compounds 8.2 The Nature of Covalent Bonding 8.3 Bonding Theories 8.4 Polar Bonds and Molecules Copyright © Pearson Education, Inc., or its affiliates. All Rights Reserved.

Do Now Draw Lewis structures for each molecule below. Then use VSEPR theory to predict their shapes. SiCl4 SCl2 CO CH2O PH3 Copyright © Pearson Education, Inc., or its affiliates. All Rights Reserved. .

Nonpolar: Electrons are shared equally. Bond Polarity Covalent Bonds Nonpolar: Electrons are shared equally. Polar: Electrons are shared unequally. Copyright © Pearson Education, Inc., or its affiliates. All Rights Reserved.

Electronegativity Values for Selected Elements Interpret Data Electronegativity – ability of an atom to attract electrons when the atom is in a compound. Electronegativity Values for Selected Elements H 2.1 Li 1.0 Be 1.5 B 2.0 C 2.5 N 3.0 O 3.5 F 4.0 Na 0.9 Mg 1.2 Al Si 1.8 P S Cl K 0.8 Ca Ga 1.6 Ge As Se 2.4 Br 2.8 Rb Sr In 1.7 Sn Sb 1.9 Te I Cs 0.7 Ba Tl Pb Bi Copyright © Pearson Education, Inc., or its affiliates. All Rights Reserved. .

Bond Polarity The electronegativity difference between two atoms tells you what kind of bond is likely to form. Electronegativity Differences and Bond Types Electronegativity difference range Type of bond Example 0.0–0.4 Nonpolar Covalent H—H (0.0) 0.4–1.9 Polar Covalent δ+ δ– δ+ δ– H—Cl (0.9) H—F (1.9) >2.0 Ionic Na+Cl– (2.1) Copyright © Pearson Education, Inc., or its affiliates. All Rights Reserved.

Sample Problem 8.3 Identifying Bond Type Which type of bond will form between the following pairs of atoms? a. N and H b. F and F c. Ca and Cl d. Al and Cl Copyright © Pearson Education, Inc., or its affiliates. All Rights Reserved.

Hydrogen Chloride (HCl) Bond Polarity Hydrogen Chloride (HCl) Hydrogen has an electronegativity of 2.1 Chlorine has an electronegativity of 3.0. This covalent bond is polar. Cl has a slight negative charge. H has a slight positive charge. δ+ δ– H—Cl Copyright © Pearson Education, Inc., or its affiliates. All Rights Reserved.

Hydrogen Chloride (HCl) Bond Polarity Hydrogen Chloride (HCl) Partial charges can be shown as clouds of electron density. They are also represented by an arrow pointing to the more electronegative atom. Copyright © Pearson Education, Inc., or its affiliates. All Rights Reserved.

Dipole: Molecule that has two poles (electrically charged regions) Bond Polarity Polar Molecule: Molecules in which electrons are unequally distributed. One end is slightly negative and the other end is slightly positive. Dipole: Molecule that has two poles (electrically charged regions) HCl is an example of a dipole Copyright © Pearson Education, Inc., or its affiliates. All Rights Reserved.

Molecule polarity depends on the shape and orientation of the bonds. Bond Polarity Molecule polarity depends on the shape and orientation of the bonds. Nonpolar Polar O C O bond polarities cancel bond polarities do not cancel Copyright © Pearson Education, Inc., or its affiliates. All Rights Reserved.

Arrange the following covalent bonds in order of decreasing polarity. Do Now Arrange the following covalent bonds in order of decreasing polarity. H-Cl H-C H-F H-O H-H S-Cl Copyright © Pearson Education, Inc., or its affiliates. All Rights Reserved. .

http://ed.ted.com/lessons/how-polarity-makes-water-behave-strangely-christina-kleinberg Copyright © Pearson Education, Inc., or its affiliates. All Rights Reserved.

Attractions Between Molecules Intermolecular Forces Weaker than ionic or covalent bonds Types Hydrogen Bonds Van der Waals Forces Dipole Interactions Dispersion Forces Copyright © Pearson Education, Inc., or its affiliates. All Rights Reserved.

Attractions Between Molecules Hydrogen bonds - a hydrogen weakly bonds to the unshared electron pair of another atom. The positive region of a water molecule attracts the negative region of another water molecule. Copyright © Pearson Education, Inc., or its affiliates. All Rights Reserved.

Attractions Between Molecules Hydrogen Bonds ~5% strength of average covalent bond. Strongest intermolecular force Determines properties of water and biological molecules Copyright © Pearson Education, Inc., or its affiliates. All Rights Reserved.

Attractions Between Molecules Dipole Interactions Polar molecules are attracted to each other Similar to, but much weaker than, ionic bonds. Copyright © Pearson Education, Inc., or its affiliates. All Rights Reserved.

Attractions Between Molecules Dispersion Forces Weakest of all molecular interactions Caused by the motion of electrons. When electrons happen to be more on one side of a molecule, they influence their neighbor’s electrons Forces increase with number of electrons Copyright © Pearson Education, Inc., or its affiliates. All Rights Reserved.

Attractions Between Molecules Dispersion Forces F and Cl have relatively few electrons and are gases at room temperature. Bromine attracts other bromine molecules enough to make it a liquid at room temperature. Iodine is a solid at room temperature. Copyright © Pearson Education, Inc., or its affiliates. All Rights Reserved.

END OF 8.4 Copyright © Pearson Education, Inc., or its affiliates. All Rights Reserved.