1. Ionic and Metallic Bonding Chapter 7

2. Introduction Ions are atoms that have either a positive or negative charge. Ions form to obtain a more stable configuration. Ionic compounds form when ions of the opposite charges interact. We can represent ions and ionic compounds using chemical symbols and formulas. Metal atoms also bond.

3. Valence Electrons The Octet Rule Formation of Cations Formation of Anions Ions Section 7.1

4. I.) Valence Electrons The electrons in the highest occupied energy level of an element’s atoms.

5. Valence electrons account for almost all the chemical behavior of an element and all chemical bonds. Elements within each group behave similarly because they have the same number of valence electrons. The number of valence electrons is related to the group numbers in the periodic table (the American and European numbering system)

6. How many valence electrons are in each atom? 1.potassium 2.carbon 3.magnesium 4.oxygen

7. Lewis Dot Structure Lewis dot structures (or electron dot structures) are diagrams that show valence electrons as dots.

8. Draw the Lewis Dot Structure for the Following Atoms. 1.potassium 2.carbon 3.magnesium 4.oxygen

9. The Octet Rule In forming compounds, atoms tend to achieve the electron configuration of a noble gas. Recall: All noble gases have eight electrons in their highest occupied energy levels. ns 2 np 6

10. Cations These are positively charged ions, resulting from a loss of an electron. Metals tends to lose electronsMetals tends to lose electrons from their highest occupied energy levels to become cations. This leaves a complete octet in the next-lowest energy level. The charge for a cation is written as a number followed by a plus sign. –Na 1+ –Ca 2+

11. Representing the Formation of Cations Atoms tend to lose their valence electrons to become cations. –Na → Na + + e - –Ca → Ca 2+ + 2e - The name of the metal is the same as the name of the ion. Most metal atoms have between 1 and 3 valence electrons they can lose. Since the number of protons do not change, a loss of an electron gives the cation a net positive charge.

12. NaNa + 1s 2 2s 2 2p 6 3s 1 1s 2 2s 2 2p 6 What noble gas does this resemble? How many e - lost? We can represent the above reaction using Lewis dot structures.

13. Cations of Transition Metals The charges of cations of a transition metal may vary. They may lose different numbers of electrons. –Some transition metals may have multiple charges. Some ions formed by transition metals do not have noble-gas electron configuration. –These ions are exception to the octet rule. –These have pseudo noble-gas configuration.

14. Examples of Cations of Transition Elements Iron Fe 2+ Fe 3+ [Ar]4s 2 3d 6 [Ar]4s 1 3d 5 [Ar]3d 5 Silver Ag + [Kr]5s 1 4d 10 [Kr]4d 10 All orbitals are filled and thus becomes relatively stable. This is the pseudo noble gas configuration. Au, Cd, and Hg also have pseudo noble gas configurations.

15. Anions These are negatively charged ions resulting from a gain of electrons. Nonmetals tend to add or share electronsNonmetals tend to add or share electrons into their highest occupied energy levels to become anions. This allows them to achieve an octet in their highest occupied energy level. The charge for an anion is written with a number followed by a negative sign. –Cl 1- –F 1-

16. Representing the Formation of Anions Atoms tend to accept electrons into their highest occupied energy levels to become anions. –e- + Cl → Cl - –e- + F → F - Name of the anion of a nonmetal ends in -ide. (chlorine = chloride ion). Since the number of protons do not change, a gain of an electron gives the anion a net negative charge.

17. ClCl - 1s 2 2s 2 2p 6 3s 2 3p 5 1s 2 2s 2 2p 6 3s 2 3p 6 How many e- gained? What noble gas does this resemble? We can represent the above reaction using Lewis dot structures.

18. 1-1- 2-2- 3-3- F - fluorideO 2- oxideN 3- nitride Cl - chlorideS 2- sulfidePO 4 3- phosphate Br - bromideSO 4 2- sulfate I - iodideCO 3 2- carbonate OH - hydroxide ClO - hypochlorite NO 3 - nitrate Some Common Anions

19. Formation of Ionic Compounds Properties of Ionic Compounds Ionic Bonds and Ionic Compounds Section 7.2 Aragonite CaCO 3 Barite BaSO 4

20. Introduction to Ionic Compounds Ionic compounds are formed from the interaction between an anion and a cation. Ionic compounds are usually composed of a metal cation and a nonmetal anion. Ionic compounds are electrically neutral: the total positive charge is equal to the total negative charge. Ionic compounds are held together by the attraction of the cations to the anions, this attraction is known as an ionic bond.

21. I.) Formation of the Ionic Bond Let’s see how this bond forms for NaCl. Na Cl 1s 2 2s 2 2p 6 3s 1 1s 2 2s 2 2p 6 3s 2 3p 5 Na + Cl - 1s 2 2s 2 2p 6 1s 2 2s 2 2p 6 3s 2 3p 6 Ionic bonds: The electrostatic forces that hold ions together in ionic compounds.

22. Write the Lewis Dot Structure for the Previous Reaction. Na + Cl Na + + Cl - (1s 2 2s 2 2p 6 3s 1 ) (1s 2 2s 2 2p 6 3s 2 3p 5 ) (1s 2 2s 2 2p 6 ) (1s 2 2s 2 2p 6 3s 2 3p 6 )

23. How Would Potassium React with Bromine? K +Br KBr

24. Representing Ionic Compounds Ions in a solid ionic compound are arranged in an orderly pattern. They do not exists as discrete units even though we write them so. We can represent the composition of a substance using chemical formulas. A formula unit is the lowest whole- number ratio of ions in an ionic compound.

25. Ions Do Not Exists as Discrete Units in an Ionic Compound Though we can write ions as individual units. Na + Cl -

26. Chemical Formulas A chemical formula shows the kinds and numbers of atoms in the smallest representative unit of a substance. For example: 1.) NaCl : sodium chloride 2.) BaF : barium fluoride

27. Formula Unit The lowest whole-number ratio of ions in an ionic compound. We use formula units because ionic compounds exists as a collection of positively and negatively charged ions arranged in repeating patterns. To determine formula units we need to keep in mind that ionic compounds must remain neutral.

28. Determining Formula Units Make sure that the charge is zero once formula units have been assigned. Example: –Na + + Cl - Na 1 Cl 1 Let’s do this for the ionic compound formed between lithium and chlorine.

29. 1.Determine the formula units for the compound formed between magnesium cations and chloride anions. 2.Determine the formula units for the compound formed between lithium cations and chloride anions.

30. Short Cut to Writing Chemical Formulas 1.Determine the charge of the cation and the anion 2.Use these charges as the subscripts for the opposing ion. 3.It’s that easy. Let’s try this for sodium oxide

31. Write the formulas for each compound: 1.barium chloride 2.magnesium oxide 3.lithium oxide 4.calcium fluoride

32. Properties of Ionic Compounds Most are crystalline solids at room temperature. Ionic compounds generally have very high melting points. Ionic compounds can conduct an electric current when melted or dissolved in water.

33. Ionic Compounds Are Solids Many are crystalline solids Components in these crystals are arranged in repeating 3-D patterns. In this arrangement, each ion is attracted strongly to each of its neighbors and repulsions are minimized.

34. Ionic Compounds Have High Melting Points There are large attractive forces between the ions. Their arrangement around each other maximizes these attractive forces and minimizes the repulsive ones. Therefore, a great deal of energy is required to break the bonds between ions in an ionic compound.

35. Ionic Compounds Conduct Electricity Ionic solutions and molten ionic compounds conduct electricity. Ions are charged and so they can conduct electricity very well. When a voltage is applied the cation migrates to the negative electrode and the anion towards the positive one, thus creating a current.

37. What are Metals? Metals are made up of closely packed cations rather than neutral atoms.

38. The Metallic Bond Metallic bonds consist of the attraction of the free- floating valence electrons for the positively charged metal ions. “Sea-of- Electrons” Model

39. “Sea-of-Electrons” Explains Metallic Properties

40. Alloys Mixtures composed of two or more elements, at least one of which is a metal. Bronze Sterling Silver

41. Alloys have properties that are often superior to those of their component elements. –Sterling Silver: (92.5% Ag & 7.5% Cu) Harder and more durable than pure silver. –Bronze: (~70% Cu & 10% Sn) Harder than copper and more easily cast. Alloys can form in different ways. –Substitutional alloy: Component atoms about the same size. –Interstitial alloy: Component atoms are quite different in size.

42. Ionic and Metallic Bonding Chapter 7 The End