2. Unit 6 Ionic Compounds

3. Remember…  The electrons in the outermost level or shell are called… –Valence electrons  You can determine the number of valence electrons in the s & p blocks by looking at the… –Group number

4. Remember…  Atoms in the same column have the same properties because they have the same… –Outer electron configuration –Number of valence electrons

5. Remember…  Lewis Dot Diagrams  A way of keeping track of valence electrons –Write the symbol –Put one dot for each valence electron –Don’t pair up until they have to X

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

7. Stable Electron Configurations  Atoms want to be stable!  Stable = noble gas configuration –8 valence electrons (s 2 & p 6 )  So…atoms will form ions to achieve that stable electron configuration

8. Atoms and ions  Atoms are electrically neutral –Same # of protons and electrons  Ions are atoms, or groups of atoms, with a charge –Different # of protons and electrons  Only electrons can be added or removed  So to become an ion, atoms gain or lose electrons

9. Remember…  Elements differ by the number of protons  Isotopes differ by the number of neutrons  Ions differ by the number of electrons

10. Forming Ions  Some atoms LOSE electron(s) to achieve a noble gas configuration  More protons than electrons so it becomes a positively charged ion  + charged ion = Cation  Occurs in metals

11. Examples of Cations  Na – 11 electrons - 1s 2 2s 2 2p 6 3s 1 –1 valence electron – VERY reactive  Na + - 10 electrons - 1s 2 2s 2 2p 6 –Noble gas configuration - STABLE K 1+ Has lost one electron Ca 2+ Has lost two electrons

12. Electron Dots For Cations  Metals have few valence electrons  They lose these electrons to become stable Ca

13. Electron Dots For Cations  Metals have few valence electrons  These will come off Ca

14. Electron Dots For Cations  Metals have few valence electrons  These will come off  Forming a positive ion (cation) Ca 2+

15. Forming Ions  Some atoms GAIN electron(s) to achieve a noble gas configuration  More electrons than protons so it becomes a negatively charged ion  Negatively charged ion = Anion  A Negative ION  Occurs in nonmetals

16. Examples of Anions  S – 16 electrons - 1s 2 2s 2 2p 6 3s 2 3p 4 –6 valence electrons = REACTIVE  S 2- - 18 electrons - 1s 2 2s 2 2p 6 3s 2 3p 6 –Noble gas configuration = STABLE F 1- Has gained one electron O 2- Has gained two electrons

17. Electron Dots For Anions  Nonmetals have several valence electrons  They will gain electrons to fill outer shell. P P 3-

18. Practice  Use electron dot diagrams to show how the following form ions  Al  Cl KK OO

19. Atomic Number # of protons # of electrons Cl Cl - K K +

20. Transition metals  WEIRD!  Form cations  Hard to predict the charge  Often will form more than 1 charge  Can’t form noble gas configuration b/c it would take too much energy  Still try to fill up orbitals

21. Examples  Zinc –1s 2 2s 2 2p 6 3s 2 3p 6 3d 10 4s 2  Zn 2+ –1s 2 2s 2 2p 6 3s 2 3p 6 3d 10 –Full 3 rd energy level  Fe 1s 2 2s 2 2p 6 3s 2 3p 6 3d 6 4s 2  Fe 2+ 1s 2 2s 2 2p 6 3s 2 3p 6 3d 5 4s 1  Fe 3+ 1s 2 2s 2 2p 6 3s 2 3p 6 3d 5

22. Naming ions  Cations keep the name of the metal –Ca calcium –Ca 2+ calcium ion  Anions change ending to –ide –Cl chlorine –Cl 1- chloride ion

23. Polyatomic ions  Groups of atoms that stick together as a unit, and have a charge  Names often end in –ate or –ite  You need to memorize the following 6: –PO 4 3- phosphate –CO 3 2- carbonate –SO 4 2- sulfate –NO 3 - nitrate –OH - - hydroxide –NH 4 + - ammonium

24. Stable Electron Configurations  Atoms want to be stable!  Stable = noble gas configuration –8 valence electrons (s 2 & p 6 )  Also called the octet rule –In forming compounds, atoms try to obtain 8 electrons in the highest energy level

25. Achieving Stability  Forming ions  Bonding with other ions to form an ionic compound

26. Ionic Bonding  Anions and cations join together to form ionic compounds (AKA salts)  The bond is formed through the transfer of electrons  Electrons are transferred to achieve noble gas configuration

27. Ionic Bonding NaCl 1+ 1-

28. Ionic Compounds (Salts)  Made up of –a positive and negative ion –a cation and an anion –a metal and a nonmetal (or polyatomic ion)  Simplest ratio of elements = formula unit

29. Properties of Ionic Compounds  Crystalline structure –A regular repeating arrangement of ions in the solid –Repeating unit is called unit cell –Structure is rigid –Ions are strongly bonded

30. Crystalline structure

31. Cubic

32. Body-Centered Cubic

33. Properties of Ionic Compounds  High melting points- because of strong forces between ions  Good conductors of electricity when dissolved in water or melted

34. Ionic Bonding  All the electrons must be accounted for! CaP

35. Ionic Bonding CaP

36. Ionic Bonding Ca 2+ P

37. Ionic Bonding Ca +2 P Ca

38. Ionic Bonding Ca 2+ P 3- Ca

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

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

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

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

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

44. Ionic Bonding Ca 3 P 2 Formula Unit

45. Practice  Use electron dot diagrams to show how the following elements make an ionic compound and write the formula unit  Mg and Cl

46. Practice  Na and N

47. Practice  Al and O

48. Writing formulas  Ionic compounds have no overall charge  So we add the correct subscripts to represent the # of atoms that balance the ions  Na + Cl - = 1:1 = NaCl  Zn 2+ S 2-

49. Writing formulas  Na 1+ O 2- –Need 2 Na 1+ to balance the O 2- –Na 2 O  Sr 2+ Cl 1-

50. Writing Formulas – Criss-Cross 1. Write the ions side by side. Fe 3+ S 2-

51. Writing Formulas – Criss-Cross 2. Draw arrows that cross each other. Fe 3+ S 2-

52. Writing Formulas – Criss-Cross 3. Put the number of charges at the ends of the arrows. Fe 3+ S 2- 23

53. Writing Formulas – Criss-Cross 4. Write the formula by using the numbers at the ends of the arrows as subscripts Fe 3+ S 2- 23 Fe 2 S 3

54. Using Polyatomic Ions  Same rules but put a bracket around the entire ion before adding the subscript  Na + OH - = 1:1 = NaOH  Mg 2+ OH - = 2:1 = Mg[OH] 2  Na + CO 3 2- = 1:2 = Na 2 CO 3  Cu 2+ PO 4 3- = 2:3 = Cu 3 [PO 4 ] 2

55. Naming Ionic Compounds  First name the cation then the anion  Cation –Usually the same name as the metal –If a transition metal, name the metal and use a roman numeral for the charge of the ion. Example, Fe 2+ or Fe 3+, iron (II) and iron (III) ions

56. Naming Ionic Compounds  Anion –Ends with –ide  If a polyatomic ion is in the compound, don’t change the name, just name it.

57. Examples  NaCl –Cation = Na (sodium) –Anion = Cl (chlorine) ide Sodium Chloride

58.  MgBr –Cation = Mg (magnesium) –Anion = Br (bromine) ide Magnesium bromide

59.  NaOH –Cation = Na (sodium) –Anion = OH (hydroxide) Sodium hydroxide  MgSO 4  Cation = Mg (magnesium)  Anion = SO 4 (sulfate) Magnesium sulfate

60.  FeCl 2 –Cation = Fe (Iron) –Anion = Cl (chlorine) ide  Which iron is this?  Cl has a -1 charge and there are 2 so the total negative charge is -2  That means there must be a positive charge of +2 for the iron Iron (II) chloride

61. Name  Formula 1.Start by writing the symbols of each element. 2.Then add the charges of each ion. 3.Use subscripts to balance the charges.

62. Name  Formula  Sodium sulfide  Na S  1+ 2-  Na 2 S

63. Ionic Bonding  Ionic bonds form between… –Metals & Nonmetals  But it is possible for nonmetals to bond to each other –Covalent bond  And for metals to bond to each other –Alloy

64. Alloys SSolutions made by dissolving metal into other elements (usually metals) MMade by melting them together and cooling them IIf the atoms of the metals are about the same size, they substitute for each other CCalled a substitutional alloy

65. Metal A Metal B +  Substitutional alloy Bronze – Copper and Tin Brass- 60 % Copper 39% Zinc and 1%Tin 18 carat gold- 75% gold, 25%Ag or Cu

66. Alloys  If the atoms of the metals are different sizes, the small one will fit into the spaces of the larger one  Called an interstitial alloy

67. Metal A +  Metal B Interstitial Alloy Steel – 99% iron 1 % C Cast iron- 96% Iron, 4%C

68. Alloys  Making an alloy is still just a mixture  Blend the properties  Designed for a purpose

69. For Your Quiz  Valence electrons  Elements vs Isotopes vs Ions  Cation vs Anion  Naming Ions  KNOW YOUR POLYATOMIC IONS  Characteristic Properties of Salts  Ionic bond forms between….  Naming compounds/ writing formulas  Alloys