Chapter Four

1. Chapter Four Ionic Compounds

2. Ions When an element loses or gains electrons, the net charge is no longer zero. A cation (positive ion) is formed when an element loses electrons An anion (negative ion) is formed when an element gains electrons

3. Periodic Trends (Periodicity) Atomic Radius Elements get larger going down a column Elements get smaller going across a row

5. Periodic Trends Ionization Energy (cation formation) Decreases going down a column Increases going across a row Electron Affinity (anion formation) Decreases going down a column Increases across a row

9. Ionic Bonds Electrons are transferred from an element with low ionization energy to elements with high electron affinity. Na transfers an electron to Cl to form NaCl. This results in a crystal structure with the same number of sodium and chloride ions and thus we say the formula is NaCl.

11. Properties of Ionic Compounds Soluble in water Conduct electricity High melting points Crystalline

12. Ions and the Octet Rule Elements gain or lose electrons in order to attain a full valence shell. (The configuration of the noble gases) We will assume that the elements all obey an octet rule (8 electrons in the valence shell) except for hydrogen (2 electrons)

14. Ionic Compound Formation Elements will form ions using the octet rule. Find the Group Number at the top of the column. If there are less than 4 electrons in outer shell, the atom will lose electrons and the ion will be positive. If there are more than 4 electrons in outer shell, the atom will gain electrons and the ion will be negative.

15. Group IA � Alkali Metals One valence electron Always +1 ions Na > Na+ + 1e-

16. Group IIA � Alkaline Earth Metals Two valence electrons Always +2 ions Mg > Mg 2+ + 2 e-

17. Group IIIA Three valence electrons Always +3 ions Al > Al 3+ + 3e-

18. Group VA Five valence electrons Gains 3 electrons to form �3 ions N + 3 e- ? N3- N < N3-

19. Group VIA Six valence electrons Gains two electrons to form �2 ions O + 2 e- ? O2- O < O2-

20. Group VIIA - Halogens Seven valence electrons Gains one electron to form �1 ions Cl + 1e- ? Cl- Cl < Cl-

21. Group VIIIA � Noble Gases Eight valence electrons Cannot gain or lose electrons Chemically inert

23. Stable Noble Gas Configuation Ions form with the same number of electrons as the noble gases. Na (11 electrons) > Na+ (10 electrons) Mg (12 electrons) > Mg 2+ (10 electrons) O (8 electrons) > O2- (10 electrons) F (9 electrons) > F- (10 electrons)

24. Isoelectronic Series Ions form with Noble gas configurations The ions with 10 electrons are: N3- O2- F- Ne Na+ Mg2+ Al3+ What are the members of the argon isoelectronic series?

25. Lewis Structures We indicate the number of valence electrons using a Lewis Structure There are four sides around the symbol Each side can hold two electrons There are a total of eight around the symbol

26. Polyatomic Ions NH4+ ammonium ion H3O+ hydronium ion OH- hydroxide ion NO3- nitrate ion CH3COO- acetate ion (C2H3O2-) HCO3- bicarbonate ion

27. CO32- carbonate ion SO42- sulfate ion HPO42- (mono)hydrogen phosphate ion H2PO4- dihydrogen phosphate ion PO43- phosphate ion

28. Formulas for Ionic Compounds Formula must be electrically neutral The number of positive charges must equal the number of negative charges The subscripts tell how many of each atom are in the formula

29. Sodium and Chlorine NaCl Calcium and Chlorine CaCl2 Aluminum and Chlorine AlCl3

30. Sodium and Sulfate (SO42-) Na2SO4 Magnesium and Hydroxide Mg(OH)2 Barium and Nitrate Ba(NO3)2

31. Potassium and Phosphate K3PO4 Magnesium and Phosphate Mg3(PO4)2 Sodium and Bicarbonate NaHCO3

32. Ammonium and Acetate NH4CH3COO Sodium and Carbonate Na2CO3 Sodium and Oxygen Na2O

33. Nomenclature Find position of first element on Periodic Table Metal with constant charge (Group IA, IIA, Al, Ag, Zn, Cd, and NH4+ Transition Metal with variable charge Non-Metal

34. Metals with Constant Charge Cation is named as element. Anion is named by changing ending to �ide� NaCl sodium chloride MgCl2 magnesium chloride Na2O sodium oxide Mg3N2 magnesium nitride (NH4)2CO3 ammonium carbonate

35. Transition Metals Roman numerals are used to designate charge on cation FeCl2 iron(II) chloride (ferrous) FeCl3 iron(III) chloride (ferric) Cu2CO3 copper(I) carbonate (cuprous) CuO copper(II) oxide (cupric)

36. Non-Metals Prefixes are used to tell how many of each atom are present in formula 1-mono 6-hexa 2-di 7-hepta 3-tri 8-octa 4-tetra 9-nona 5-penta 10-deca

37. CO carbon monoxide CO2 carbon dioxide CCl4 carbon tetrachloride XeF6 xenon hexafluoride

38. Acids and Bases Acid � A substance that donates protons (H+) in water Common Acids: acetic, CH3COOH carbonic, H2CO3 hydrochloric, HCl nitric, HNO3 phosphoric, H3PO4 sulfuric, H2SO4

39. Base � A substance that provides hydroxide ion (OH-) in solution Common Bases Sodium hydroxide, NaOH Potassium hydroxide, KOH Barium hydroxide, Ba(OH)2

40. Dissociation in Water Soluble substance dissolve in water by dissociation: NaCl > Na+ + Cl- CaCl2 > Ca2+ + 2Cl- HCl > H+ + Cl- NaOH > Na+ + OH-