2. Chapter 8 Ionic Bonding

3. Keeping Track of Electrons l The electrons responsible for the chemical properties of atoms are those in the outer energy level. l Valence electrons - The s and p electrons in the outer energy level. l Core electrons -those in the energy levels below.

4. Keeping Track of Electrons l Atoms in the same column l Have the same outer electron configuration. l Have the same valence electrons. l Easily found by looking up the group number on the periodic table. l Group 2A - Be, Mg, Ca, etc.- l 2 valence electrons

5. Electron Dot diagrams l A way of keeping track of valence electrons. l How to write them l Write the symbol. l Put one dot for each valence electron l Don’t pair up until they have to X G. N. Lewis 1875 - 1946

6. The Electron Dot diagram for Nitrogen l Nitrogen has 5 valence electrons. l First we write the symbol. N l Then add 1 electron at a time to each side. l Until they are forced to pair up.

7. Write the electron dot diagram for l Na l Mg lClC lOlO lFlF l Ne l He

8. Electron Configurations for Cations l Metals lose electrons to attain noble gas configuration. l They make positive ions. l If we look at electron configuration it makes sense. l Na 1s 2 2s 2 2p 6 3s 1 - 1 valence electron l Na + 1s 2 2s 2 2p 6 -noble gas configuration

9. Electron Dots For Cations l Metals will have few valence electrons Ca

10. Electron Dots For Cations l Metals will have few valence electrons l These will come off Ca

11. Electron Dots For Cations l Metals will have few valence electrons l These will come off l Forming positive ions Ca +2

12. Electron Configurations for Anions l Nonmetals gain electrons to attain noble gas configuration. l They make negative ions. l If we look at electron configuration it makes sense. l S 1s 2 2s 2 2p 6 3s 2 3p 4 - 6 valence electrons l S -2 1s 2 2s 2 2p 6 3s 2 3p 6 -noble gas configuration.

13. Electron Dots For Anions l Nonmetals will have many valence electrons. l They will gain electrons to fill outer shell. P P -3

14. Stable Electron Configurations l All atoms react to achieve noble gas configuration. l Noble gases have 2 s and 6 p electrons. l 8 valence electrons. l Also called the octet rule. Ar

15. Ionic Bonding l Anions and cations are held together by opposite charges. MovieMovie l Ionic compounds (metal plus nonmetal) are called salts. l Covalent bonds are between nonmetals. l Simplest ratio in ionic bonds is called the formula unit. l The bond is formed through the transfer of electrons. l Electrons are transferred to achieve noble gas configuration. MovieMovie

16. Ionic Bonding NaCl

17. Ionic Bonding Na + Cl -

18. Ionic Bonding l All the electrons must be accounted for! CaP

19. Ionic Bonding CaP

20. Ionic Bonding Ca +2 P

21. Ionic Bonding Ca +2 P Ca

22. Ionic Bonding Ca +2 P -3 Ca

23. Ionic Bonding Ca +2 P -3 Ca P

24. Ionic Bonding Ca +2 P -3 Ca +2 P

25. Ionic Bonding Ca +2 P -3 Ca +2 P Ca

26. Ionic Bonding Ca +2 P -3 Ca +2 P Ca

27. Ionic Bonding Ca +2 P -3 Ca +2 P -3 Ca +2

28. Ionic Bonding Ca 3 P 2 Formula Unit MovieMovie

29. Properties of Ionic Compounds l Crystalline structure. l A regular repeating arrangement of ions in the solid. l Ions are strongly bonded. l Structure is rigid. l High melting points- because of strong forces between ions.

30. Crystalline Structure

31. Do they Conduct? l Conducting electricity is allowing charges to move. l In a solid, the ions are locked in place. l Ionic solids are insulators. l When melted, the ions can move around. l Melted ionic compounds conduct. l First get them to 800ºC. l Dissolved in water they conduct.

32. Metallic Bonds l How atoms are held together in 3-D solid or a crystal lattice. l Metals hold onto their valence electrons very weakly. l Think of them as positive ions floating in a sea of electrons. Electrons are considered “delocalized”

33. Sea of Electrons ++++ ++++ ++++ l Electrons are free to move through the solid. l Metals conduct electricity.

34. Metals are Malleable and Ductile l Malleable - Hammered into shape (compression force). l Ductile - drawn into wires (tension force).

35. Malleable (compression) ++++ ++++ ++++

36. ++++ ++++ ++++ l Electrons allow atoms to slide by.

37. Ionic solids are brittle +-+- + - +- +-+- + - +-

38. + - + - + - +- +-+- + - +- l Strong Repulsion breaks crystal apart.

39. Alloys l We use lots of metals every day, but few are pure metals l Alloys - mixtures of 2 or more elements, at least 1 is a metal l made by melting a mixture of the ingredients, then cooling l Brass: an alloy of Cu and Zn l Bronze: Cu and Sn MovieMovie

41. Why use alloys? l Properties often superior to element l Sterling silver (92.5% Ag, 7.5% Cu) is harder and more durable than pure Ag, but still soft enough to make jewelry and tableware l Steels are very important alloys –corrosion resistant, ductility, hardness, toughness, cost