2. COVALENT BONDING

3. Covalent Bond Covalent bonds result in discrete molecules. Cl 2 H2OH2O NH 3

4. Covalent Compounds l A molecule is an uncharged group of two or more atoms held together by covalent bonds. l Covalent compounds occur between two nonmetals or a nonmetal and hydrogen.

5. How Does H 2 Form? l The nuclei repel ++

6. How Does H 2 Form? ++ l But they are attracted to electrons. l They share the electrons.

7. Covalent Compounds l The attraction of two atoms for a shared pair of electrons is called a covalent bond. l In a covalent bond, atoms share electrons and neither atom has an ionic charge.

8. Covalent Bonds l Covalent bonds occur between 2 nonmetals because nonmetals hold onto their valence electrons. l They can’t give away electrons to bond, yet, they still want noble gas configuration.

9. Covalent Bonds l They get it by sharing valence electrons with each other. l By sharing both atoms get to count the electrons toward noble gas configuration.

10. Covalent Bonding l Fluorine has seven valence electrons. F

11. Covalent Bonding l A second fluorine atom also has seven valence electrons. F F

12. Covalent Bonding l The fluorine atoms will share their lone electrons. F F

13. Covalent Bonding FF l The fluorine atoms are getting closer together in order to share their lone electrons.

14. Covalent Bonding FF

15. FF

16. FF

17. l Both end with full orbitals. FF

18. Covalent Bonding l The fluorine on the right has 8 valence electrons! FF 8 valence electrons

19. Covalent Bonding l The fluorine on the left has 8 valence electrons! FF 8 valence electrons

21. Water H Each hydrogen has 1 valence electron. Each hydrogen wants 1 more.

22. Water O The oxygen has 6 valence electrons. The oxygen wants 2 more.

23. Water l Hydrogen and oxygen share to make each other happy. l The first hydrogen is happy, but the oxygen still wants one more electron. H O

24. Water l A second hydrogen attaches. H O H

25. Question l Do atoms that share a covalent bond have an ionic charge? (No, the atoms share electrons and neither atom has a charge.)

26. Chemical Bond l Transferring e - l Sharing e -

27. METALLIC BONDING

28. Metallic Bonds l The bonding in metals is explained by the electron sea model, which proposes that the atoms in a metallic solid contribute their valence electrons to form a “sea” of electrons that surrounds metallic cations.

29. Metallic Bonds l These delocalized electrons are not held by any specific atom and can move easily throughout the solid.

30. Metallic Bonds Metal atoms release their valence electrons into a sea of electrons shared by all of the metal atoms. The bond that results from this shared pool of valence electrons is called a metallic bond.

31. Metallic Bonds l Metals hold onto their valence electrons very weakly. l Think of them as positive ions floating in a sea of electrons.

32. Alloys l A mixture of elements that has metallic properties is called an alloy.

33. Metallic Bond: A Sea of Electrons

34. Metallic Bonds: Mellow dogs with plenty of bones to go around.