1. Section 12.1 Characteristics of Chemical Bonds 1.To learn about ionic and covalent bonds and explain how they are formed 2.To learn about the polar covalent bond 3.To understand the nature of bonds and their relationship to electronegativity 4.To understand bond polarity and how it is related to molecular polarity Objectives

2. Section 12.1 Characteristics of Chemical Bonds A. Types of Chemical Bonds Bond – force that holds groups of atoms together and makes them function as a unit Bond energy – energy required to break a chemical bond

3. Section 12.1 Characteristics of Chemical Bonds A. Types of Chemical Bonds Ionic compound results when a metal reacts with a nonmetal Ionic Bonding (a) (b)

4. Section 12.1 Characteristics of Chemical Bonds A. Types of Chemical Bonds A covalent bond results when electrons are shared by nuclei Covalent Bonding

5. Section 12.1 Characteristics of Chemical Bonds A. Types of Chemical Bonds A polar covalent bond results when electrons are shared unequally by nuclei Covalent Bonding –One atom attracts the electrons more than the other atom

6. Section 12.1 Characteristics of Chemical Bonds B. Electronegativity Electronegativity – the relative ability of an atom in a molecule to attract shared electrons to itself –Increases from left to right across a period –Decreases down a group of representative elements

7. Section 12.1 Characteristics of Chemical Bonds B. Electronegativity The polarity of a bond depends on the difference between the electronegativity values of the atoms forming the bond

8. Section 12.1 Characteristics of Chemical Bonds B. Electronegativity

9. Section 12.1 Characteristics of Chemical Bonds C. Bond Polarity and Dipole Moments A dipole moment results when a polar molecule has a center for positive charge separate from a center for negative charge

10. Section 12.1 Characteristics of Chemical Bonds C. Bond Polarity and Dipole Moments Water molecule dipole moment

11. Section 12.1 Characteristics of Chemical Bonds C. Bond Polarity and Dipole Moments The polarity of water affects its properties –Causes water to remain liquid at higher temperature –Permits ionic compounds to dissolve in it