Ionic Compounds Chapter 8

1. Ionic Compounds Chapter 8

2. Forming Chemical Bonds How do the infinite number of compounds that we see in the world around form from the 92 naturally occurring elements?

3. CHEMICAL BONDS

4. 1. What is a chemical bond? The force that holds two atoms together. Chemical bonds form from the attraction between the protons and electrons in covalent bonds. In ionic bonds the attraction is between the positive and negative ions involved.

5. 2. What do we call the outermost electrons involved in chemical bonding? Valence electrons

6. 3. What are some ways that electron dot diagrams are used? They are useful to show valence electrons and to show how two or more atoms may bond.

7. 4. What is ionization energy? A measure of how easily an electron can be removed.

8. 5. What is electron affinity? A measure of the attraction an atom has for electrons.

9. Where do we find high ionization energy and high electron affinity?

10. Where do we find high ionization energy and high electron affinity? Halogens

11. Where do we find high ionization energy and low electron affinity?

12. Where do we find high ionization energy and low electron affinity? Noble gases

13. Where do we find low ionization energy and low electron affinity?

14. Where do we find low ionization energy and low electron affinity? Alkali metals

15. 6. Why do we have these differences in reactivity?

16. 6. Why do we have these differences in reactivity? The most stable electron configuration is a full valence shell. Atoms will gain lose or share electrons in order to follow the octet rule.

17. 7. What is the octet rule? Atoms tend to gain lose or share electrons in order to acquire a full valence shell. This is usually 8 valence electrons. Hydrogen and helium only have 2.

18. Formation of Positive Ions

19. 8. When does a positive ion form? When an atom loses one or more electrons.

20. 8. When does a positive ion form? When an atom loses one or more electrons.

21. 9. What do we call a positively charged ion? Cation

22. 10. What types of ions do transition metals form? They are all cations, but they show a lot of variation. The cations of the metals can have various charges.

23. 11. What do we call the stable electron configuration that transition metals take that does not resemble the noble gases? Pseudo-noble gas configuration. For example, Zn will form an ion with a +2 charge [Ar] 3d10

24. Formation of negative ions

25. Nonmetals tend to gain electrons.

26. 12. When does a negative ion form? When an atom gains electrons.

27. 13. What do we call a negatively charged ion? anion

28. 14. When an atom becomes an ion its name changes. How do the names of ions differ from the atom from which they were formed? The cation is the name of the element with the word ion added. The anion is the name of the element with the ending changed to –ide.

29. For example; Sodium becomes Sodium ion. Chlorine becomes Chloride.

30. Section 2: The Formation and Nature of Ionic Bonds

31. 15. What is an ionic bond? A bond formed between oppositely charged ions.

32. 16. Why do ionic bonds form? Because of the electrostatic attraction between oppositely charged ions.

33. 17. What type of ionic compounds are formed from ionic bonds? If the ionic bond includes oxygen as its nonmetal anion it is an oxide. Most other ionic compounds create a salt from a metallic cation and a non-metalic anion.

34. 18. What is a binary ionic compound? An ionic compound that contains only two elements. i.e., NaCl KI MgO Na2O

35. 19. All ionic compounds are neutral. What does that mean with regard to the number of electrons gained or lost? The number of electrons gained by the non-metal must equal the number of electrons lost by the metal.

36. Properties of Ionic Compounds

37. 20. What are ionic crystals? Ionic crystals are formed when the positive and negative ions are packed into a regular repeating pattern that balances the forces of attraction and repulsion between ions.

38. 21. Do ionic compounds exist as single units? No Large numbers of positive and negative ions exist together in a crystal lattice.

39. 22. What is a crystal lattice? A three dimensional geometric arrangement of particles. The crystal lattice causes ionic crystals to vary in size and shape due the sizes and relative numbers of ions in the crystal lattice arrangement.

41. 23. Because ionic bonds are very strong, ionic compounds tend to have certain properties. 1.) high melting point 2.) tend to be hard 3.) tend to be brittle 4.) In the solid state, ionic compounds are not good conductors of electricity. 5.) In aqueous solutions they are good conductors of electricity.

42. Note- When dissolved in water ionic compounds disassociate into positive and negative ions (cations and anions) This allows the ions to move freely. Dissolved ionic compounds are very good conductors of electricity.

43. 24. What is an electrolyte? An ionic compound whose aqueous solutions conduct an electric current.

44. 25. In a chemical reaction if energy is absorbed the reaction is endothermic. If the energy is released the reaction is exothermic.

45. 26. The formation of ionic compounds from cations and anions is always exothermic.

46. 27. What is lattice energy? The energy required to separate one mole of ions in an ionic compounds.

48. 28. What is reflected in the lattice energy? The stronger the forces holding the ions together the more negative the lattice energy. A very negative lattice energy means the ions are held together very forcefully. Continued

49. 28 continued * Smaller ions generally have more negative values because the nucleus of the cation is closer to the electrons of the anion. continued

50. 28 continued *The ionic bond formed between ions with larger positive or negative values have more negative lattice energies.