The document summarizes key concepts about covalent bonds, including how they form through the sharing of valence electrons between atoms to achieve stability. It discusses ionic vs. covalent bonds, how covalent bonds are represented using Lewis dot structures, and how the octet rule determines bonding patterns for atoms in different groups on the periodic table. Examples of writing Lewis dot structures for several diatomic and polyatomic molecules are provided.

1. Chapter 9 Covalent Bonds pp. 240 - 267

2. Review.. What is a chemical bond? Force that holds two atoms together What is an ionic bond? An electrostatic force that holds oppositely charged particles together in an ionic compound Forms when….? What are atoms and compounds always trying to achieve? Stability Complete set of valence electrons…

3. What is a covalent bond? Chemical bond that results from sharing of valence electrons

4. Which bond is stronger? Ionic vs. Covalent Remember…. Ionic compounds are in a crystal lattice…many ions are bonded together in a crystal lattice Covalent compounds are neutral and often found in the form of individual molecules Ionic bonds are stronger than covalent bonds

5. How are covalent bonds formed? Charge of nucleus? Charge of electron cloud? What happens when 2 fluorine atoms approach each other? Covalent bond occurs at “Point of maximum attraction” Attractive forces of nucleus for electrons and repulsive forces of electrons in each atom balance out What would happen if the atoms kept moving closer?

6. What is a Molecule? Compound made when two or more atoms bond together covalently Diatomic molecules In nature, sometimes two atoms of the same element are more stable when they are covalently bonded than the individual atom alone… BrINClHOF Br 2 I 2 N 2 Cl 2 H 2 O 2 F 2

7. Types of electrons in molecule Look at fluorine What is the electron configuration? 1s 2 2s 2 2p 5 How many Valance electrons? 7 Dot Structure? What would two F atoms look like covalently bonded?

8. BONDING PAIRS are electrons involved in the covalent bond (shared electrons) The pairs of electrons that are NOT involved in the covalent bond are called the LONE PAIRS (unshared electrons) What are the lone pairs in…

9. In the fluorine molecule… How many bonding pairs are there in each? 1 How many lone pairs are there each? 3

10. Lewis Dot Diagrams When writing out molecules… Bonding pairs can be represented by the electrons themselves or by a single line If there is more than one bonding pair, two lines are used Up to four lines can be used EACH LINE REPRESENTS A BONDING PAIR OF ELECTRONS IN A MOLECULE 1 line=2 electrons Lines represent bonding pairs…you must still draw out lone pairs

11. 3 basic rules Sum up valence electrons of all atoms in the molecule Use a pair of electrons to form a bond between atoms…use a line to represent bond Arrange remaining electrons to satisfy the duet rule for hydrogen and the octet rule for other atoms (Verify that each atom has a complete set of electrons )

12. Elements is group 7A have how many valence electrons? How many electrons would they share in a covalent bond with an atom in group 7A? How many covalent bonds do are formed between bonding atoms in 7A? Elements in group 6A have how many valence electrons? How many electrons would they have to share in a covalent bond with another atom in group 6A? How many covalent bonds do are formed between bonding atoms in 6A?

13. Elements in group 5A have how many valence electrons? How many electrons would they have to share in a covalent bond with another atom in group 5A? How many covalent bonds do are formed between bonding atoms in 5A? Elements in group 4A have how many valence electrons? How many electrons would they have to share in a covalent bond to be stable? How many covalent bonds are formed between bonding atoms in group 4A?

14. Writing Chemical Equations showing covalent bond formation See board…

15. Classwork…to turn in… 1. PH 3 2. H 2 S 3. HCl 4. CCl 4 5. SiH 4 6. HF 7. N 2 8. CH 4 9. CF 4 Show the formation of the following molecules…your final answer should be the correct Lewis Dot Structure