2. CHEM 5013 Applied Chemical Principles Chapter Seven Professor Bensley Alfred State College

3. Chapter Objectives Describe the differences between ionic and covalent chemical bonds and predict which type of bond forms a chemical compound. Describe the differences between ionic and covalent chemical bonds and predict which type of bond forms a chemical compound. Use electron configurations to explain why metals tend to form cations, whereas nonmetals tend to form anions. Use electron configurations to explain why metals tend to form cations, whereas nonmetals tend to form anions.

4. Chapter Objectives Use Lewis symbols to represent the transfer of electron(s) from cations to anions in ionic species. Use Lewis symbols to represent the transfer of electron(s) from cations to anions in ionic species. Write Lewis electron structures for molecules and ions. Write Lewis electron structures for molecules and ions. Describe chemical bonding using a model based on the overlap of atomic orbitals. Describe chemical bonding using a model based on the overlap of atomic orbitals.

5. Ionic Bonding REVIEW – What is an ion? REVIEW – What is an ion? Ionic Bonds:

6. Ionic Bonds Example: NaCl Na = __ valence electrons? +Cl = __ valence electrons? What happens to the valence electrons? FORMS 

7. Ionic Bonds You can simplify the equation using You can simplify the equation using Lewis Electron-Dot Symbols Do you remember what the Group number indicates?

8. Lewis Electron-Dot Symbols Use Lewis Dot Symbols to represent the transfer of electrons in forming Calcium Oxide, CaO, from atoms. Ca O + Ca 2+ + O 2-

9. Lewis Electron-Dot Symbols Use Lewis Dot Symbols to represent the formation of Calcium Chloride. Use Lewis Dot Symbols to represent the formation of Calcium Chloride.

10. Properties of Ionic Substances Typically high melting solids Typically high melting solids When they melt into a liquid, or if you have a solution, it consists mainly of ions which conduct electricity, called electrolytes. When they melt into a liquid, or if you have a solution, it consists mainly of ions which conduct electricity, called electrolytes.

11. Electron Configurations of Ions Example Example 1. Write the electron configuration and Lewis symbol for Ca 2+ 2. Write the electron configuration and Lewis symbol for S 2-

12. Covalent Bonds Covalent Bonds:

13. Covalent Bonds Consider H 2 : H H Or HCl: HCl : : :

14. Lewis Dot Formulas Definition: Definition: : H : : : Cl Bonding Pair Lone Pair

15. Octet Rule – Covalent Compounds Atoms in covalent compounds obtain noble gas configurations by sharing electrons. Atoms in covalent compounds obtain noble gas configurations by sharing electrons. Octet Rule: Octet Rule: Exception: Exception:

16. Double Bonds Double Bonds Covalent bond in which 2 pairs of electrons are shared by 2 atoms (usually with C,N,O or S) Covalent bond in which 2 pairs of electrons are shared by 2 atoms (usually with C,N,O or S) Example: Carbon dioxide CO 2 Example: Carbon dioxide CO 2 Triple Bonds Triple Bonds Covalent bond in which 3 pairs of electrons are shared by 2 atoms (usually with C or N) Covalent bond in which 3 pairs of electrons are shared by 2 atoms (usually with C or N) Example: Acetylene C 2 H 2 Example: Acetylene C 2 H 2 Multiple Bonds

17. Keeping Track of Bonding: Lewis Structures Step 1 - Count the total valence electrons in the molecule or ion. Step 1 - Count the total valence electrons in the molecule or ion. Step 2 - Draw the skeletal structure of the molecule. Step 2 - Draw the skeletal structure of the molecule. Step 3 – Place single bonds between all connected atoms in the structure by drawing a bonding pair between them. Step 3 – Place single bonds between all connected atoms in the structure by drawing a bonding pair between them.

18. Keeping Track of Bonding: Lewis Structures Step 4 - Place the remaining valence electrons not accounted for in Step 3 on individual atoms until the Octet Rule is satisfied. Place electrons as lone pairs whenever possible. Step 4 - Place the remaining valence electrons not accounted for in Step 3 on individual atoms until the Octet Rule is satisfied. Place electrons as lone pairs whenever possible. Step 5 – Create multiple bonds by shifting lone pairs into bonding positions as needed for any atoms that do not have a full octet of valence electrons. Step 5 – Create multiple bonds by shifting lone pairs into bonding positions as needed for any atoms that do not have a full octet of valence electrons.

19. Lewis Structure Examples Write the Lewis Structures for the following: Write the Lewis Structures for the following: 1. OF 2 2. H 2 O 3. Carbon monoxide