1. Sec. 8.4: Polar Bonds and Molecules When both atoms forming a bond are the same element they have an electronegativity difference of “0”. This means that the shared pair of electrons are “evenly shared”. This type of bond is called a Non-polar Covalent Bond. A non-polar covalent bond occurs when the electronegativity difference is less than 0.5.

2. + + Hydrogen Chloride (HCl) 1s 2 2s 2 2p 6 3s 2 3p 6 1s 2 *Unfair sharing of a pair of electrons results in “polar” covalent bonding. The pair of shared electrons is positioned closer to the more electronegative atom. This causes each atom to have a slight charge. Sec. 8.4: Polar Bonds and Molecules

3. O H H δ- δ+ A polar bond occurs when the electronegativity difference between bonding atoms is between.5 and 1.7. If polar bonding causes the molecule to exhibit slightly charged ends, the molecule is then termed “Polar”. 2.2 3.5 Sec. 8.4: Polar Bonds and Molecules

4. COO 2.53.5 δ- Answer:_________ NO Carbon dioxide does have polar bonds, however its ends are of the same charge (slightly negative). Sec. 8.4: Polar Bonds and Molecules

5. HF 2.2 4.0 δ-δ+ *Hydrogen fluoride is a polar molecule due to its polar bond. Sec. 8.4: Polar Bonds and Molecules

6. δ- δ+ H 2 O is a polar molecule. Due to this fact water exhibits a fairly high boiling temperature (100 0 C). The slightly positive hydrogen is attracted to the slightly negative oxygen on an adjacent water molecule. *An attraction between molecules is called an intermolecular force. Sec. 8.4: Polar Bonds and Molecules

7. *Intermolecular forces are attractions between molecules. All molecules have some attraction for other molecules. These attractions may range from very weak to quite strong. 1. Dipole-Dipole Forces: δ- δ+ This type of force occurs between polar molecules. Polar molecules are considered to be “Dipoles” (meaning “opposite ends”) 2. Hydrogen Bond: The hydrogen bond is really “not” a bond at all. Rather it is a type of dipole-dipole force between molecules that have a hydrogen atom bonded to one of the following atoms (O, N, or F). The hydrogen will be attracted to the (O, N, or F) on the other molecule and vice versa. Hydrogen Bond Sec. 8.4: Polar Bonds and Molecules

8. HClH 1. Dipole-dipole attraction between 2 hydrogen chloride molecules? Answer:________ 2. Dipole-dipole attraction between 2 ammonia molecules? H H H N H H H N Answer:________ 3. Dipole-dipole attraction between a hydrogen chloride molecule and a water molecule? HCl Answer:________ NO Yes NO H H O

9. 3. Ion-Dipole Forces: Na + Cl - Na + Cl - Na + Cl - Na + Cl - Sodium Chloride Crystal (Held together by ionic bonds) Water (a dipole) has an intermolecular force attracting it to both chloride and sodium ions. Sec. 8.4: Polar Bonds and Molecules

10. 4. Dipole-Induced Dipole Forces: When water (a dipole) comes close to an oxygen molecule (nonpolar) the electron distribution of the oxygen molecule is distorted by the force exerted by the polar water molecule. The result is an induced dipole moment occurring on the oxygen molecule. The molecules in turn are attracted to each other by an intermolecular force. Sec. 8.4: Polar Bonds and Molecules

11. 5. London Dispersion Forces: The last type of intermolecular force occurs between two nonpolar molecules that have become momentary dipoles. This occurs when one molecule approaches another causing their electron clouds to be distorted. The momentary distortion of the electron clouds causes the molecules to have a rather weak intermolecular force between them. Sec. 8.4: Polar Bonds and Molecules

12. Name the type of attraction between each pair of molecules. (dipole-dipole, hydrogen bond, dipole-ion, dipole-induced dipole or London dispersion) 1._________________ 2._________________ 3._________________ 4._________________ HBr H H S HHHH HH H H N O H H F Dipole-Dipole London dispersion Hydrogen Bond dipole-induced dipole Sec. 8.4: Polar Bonds and Molecules

13. * Solids can be described in terms of the types of particles in them and the types of chemical bonding between the particles. 1.Ionic solids: 2.Covalent Network Solids: 3.Metallic Crystals: 4.Covalent Molecular Crystals: Consists of positive and negative ions arranged in a regular pattern. Consists of single atoms covalently bonded to its nearest neighboring atom. Consists of metal atoms surrounded by a sea of valence electrons. Consists of covalently bonded molecules held together by intermolecular forces. Sec. 8.4: Polar Bonds and Molecules