These are a mix of two PPTs.

1. These are a mix of two PPTs. • Take some time and review each slide. • These are excellent aids if you feel you need some extra help. • As always, email me or come in for some help in the morning or afternoon- just email me before hand. • Think about the rock salt you studied in class today- metals plus non-metals make SALTS!

2. “Ionic Bonding”Ch. 7 Ionic Bondingandnaming of Ionic Bonds (part of ch. 10)

3. Ions • OBJECTIVES: • Determine the number of valence electrons in an atom of a representative element. • Explain how the octet rule applies to atoms of metallic and nonmetallic elements. • Describe how cations form. • Explain how anions form.

4. Valence Electrons are… • The electrons responsible for the chemical properties of atoms, and are those in the outer energy level. • Think protons: identity & electrons: behavior • Valence electrons - The s and p electrons in the outer energy level • outer most electrons • highest occupied energy level • Core or Inner electrons-those in the energy levels below.

5. Keeping Track of Electrons • Atoms in the same column... • Have the same outer electron configuration. • Have the same valence electrons. • The number of valence electrons are easily determined: the group number for a representative element • Group 2A: Be, Mg, Ca, etc. • have 2 valence electrons

6. X Electron Dot diagrams are… • A way of showing & keeping track of valence electrons. • How to write them? • Write the symbol - it represents the nucleus and inner (core) electrons • Put one dot for each valence electron (8 maximum) • They don’t pair up until they have to (Hund’s rule)

7. Nitrogen has 5 valence electrons to show. • First we write the symbol. N • Then add 1 electron at a time to each side. • Now they are forced to pair up. • We have now written the electron dot diagram for Nitrogen. The Electron Dot diagram for Nitrogen

8. The Octet Rule • In 1916, Gilbert Lewis used this fact to explain why atoms form certain kinds of ions and molecules • The Octet Rule: in forming compounds, atoms tend to achieve a noble gas configuration; 8 in the outer level is stable • Each noble gas (except He) has 8 electrons in the outer level

9. Formation of Cations • Metals lose electrons to attain a noble gas configuration. • They make positive ions (cations) • If we look at the electron configuration, it makes sense to lose electrons: • Na 1s22s22p63s1 1 valence electron • Na1+1s22s22p6 This is a noble gas configuration with 8 electrons in the outer level.

10. Ca Electron Dots For Cations • Metals will have few valence electrons (usually 3 or less); calcium has only 2 valence electrons

11. Ca Electron Dots For Cations • Metals will have few valence electrons • Metals will lose the valence electrons

12. Electron Dots For Cations • Metals will have few valence electrons • Metals will lose the valence electrons • Forming positive ions Ca2+ This is named the calcium ion. NO DOTS are now shown for the cation.

13. =Sc3+ Sc Electron Dots For Cations • Let’s do Scandium, #21 • The electron configuration is: 1s22s22p63s23p64s23d1 • Thus, it can lose 2e- (making it 2+), or lose 3e- (making 3+) Sc = Sc2+ Scandium (III) ion Scandium (II) ion

14. Electron Dots For Cations • Let’s do Silver, element #47 • Predicted configuration is: 1s22s22p63s23p64s23d104p65s24d9 • Actual configuration is: 1s22s22p63s23p64s23d104p65s14d10 Ag = Ag1+ (can’t lose any more, charges of 3+ or greater are uncommon)

15. Electron Dots For Cations • Silver did the best job it could, but it did not achieve a true Noble Gas configuration • Instead, it is called a “pseudo-noble gas configuration”

16. Electron Configurations: Anions • Nonmetals gain electrons to attain noble gas configuration. • They make negative ions (anions) • S = 1s22s22p63s23p4 = 6 valence electrons • S2- = 1s22s22p63s23p6 = noble gas configuration. • Halide ions are ions from chlorine or other halogens that gain electrons

17. P Electron Dots For Anions • Nonmetals will have many valence electrons (usually 5 or more) • They will gain electrons to fill outer shell. P3- This is called the phosphide ion

18. Ar Stable Electron Configurations • All atoms react to try and achieve a noble gas configuration. • Noble gases have 2 s and 6 p electrons. • 8 valence electrons = already stable! • This is the octet rule (8 in the outer level is particularly stable).

19. Ionic Bonds and Ionic Compounds • OBJECTIVES: • Explain the electrical charge of an ionic compound. • Describe three properties of ionic compounds.

20. Ionic Bonding • Anions and cations are held together by opposite charges. • Ionic compounds are called salts. • Simplest ratio of elements in an ionic compound is called the formula unit. • The bond is formed through the transfer of electrons. • Electrons are transferred to achieve noble gas configuration.

21. Na Cl Ionic Bonding The metal (sodium) tends to lose its one electron from the outer level. The nonmetal (chlorine) needs to gain one more to fill its outer level, and will accept the one electron that sodium is going to lose.

22. Na+ Cl - Ionic Bonding Note: Remember that NO DOTS are now shown for the cation!

23. Ca P Ionic Bonding Lets do an example by combining calcium and phosphorus: • All the electrons must be accounted for, and each atom will have a noble gas configuration (which is stable).

24. Ca P Ionic Bonding

25. Ca2+ P Ionic Bonding

26. Ca2+ P Ca Ionic Bonding

27. Ca2+ P 3- Ca Ionic Bonding

28. Ca2+ P 3- Ca P Ionic Bonding

29. Ca2+ P 3- Ca2+ P Ionic Bonding

30. Ca Ca2+ P 3- Ca2+ P Ionic Bonding

31. Ca Ca2+ P 3- Ca2+ P Ionic Bonding

32. Ca2+ Ca2+ P 3- Ca2+ P 3- Ionic Bonding

33. = Ca3P2 Formula Unit Ionic Bonding This is a chemical formula, which shows the kinds and numbers of atoms in the smallest representative particle of the substance. For an ionic compound, the smallest representative particle is called a: Formula Unit

34. Properties of Ionic Compounds • Crystalline solids - a regular repeating arrangement of ions in the solid: • Ions are strongly bonded together. • Structure is rigid. • High melting points • Coordination number- number of ions of opposite charge surrounding it

35. Coordination Numbers: Both the sodium and chlorine have 6 NaCl Both the cesium and chlorine have 8 CsCl Each titanium has 6, and each oxygen has 3 TiO2

36. Do they Conduct? • Conducting electricity means allowing charges to move. • In a solid, the ions are locked in place. • Ionic solids are insulators. • When melted, the ions can move around. • Melted ionic compounds conduct. • NaCl: must get to about 800 ºC. • Dissolved in water, they also conduct (free to move in aqueous solutions)

37. The ions are free to move when they are molten (or in aqueous solution), and thus they are able to conduct the electric current.

38. Resources • Stephen L. Cotton - Charles Page High School • http://www.cottonchemistry.bizland.com/chemistry/chemindex.htm

39. Section 7-1 Section 7.1 Ion Formation • Define a chemical bond. octet rule: atoms tend to gain, lose, or share electrons in order to acquire eight valence electrons • Describe the formation of positive and negative ions. • Relate ion formation to electron configuration. chemical bond cation anion Ions are formed when atoms gain or lose valence electrons to achieve a stable octet electron configuration.

40. Section 7-1 Valence Electrons and Chemical Bonds • A chemical bond is the force that holds two atoms together. • Chemical bonds form by the attraction between the positive nucleus of one atom and the negative electrons of another atom.

41. Section 7-1 Valence Electrons and Chemical Bonds (cont.) • Atom’s try to form the octet—the stable arrangement of eight valence electrons in the outer energy level—by gaining or losing valence electrons.

42. Section 7-1 Positive Ion Formation • A positively charged ion is called a cation. • This figure illustrates how sodium loses one valence electron to become a sodium cation.

43. Section 7-1 Positive Ion Formation (cont.) • Metals are reactive because they lose valence electrons easily.

44. Section 7-1 Positive Ion Formation (cont.) • Transition metals commonly form 2+ or 3+ ions, but can form greater than 3+ ions. • Other relatively stable electron arrangements are referred to as pseudo-noble gas configurations.

45. Section 7-1 Negative Ion Formation • An anionis a negatively charged ion. • The figure shown here illustrates chlorine gaining an electron to become a chlorine ion.

46. Section 7-1 Negative Ion Formation (cont.) • Nonmetal ions gain the number of electrons required to fill an octet. • Some nonmetals can gain or lose electrons to complete an octet.

47. Section 7-1 Section 7.1 Assessment Oxygen gains two electrons to form what kind of ion? A.1– anion B.2– anion C.1+ cation D.2+ cation • A • B • C • D

48. Section 7-1 Section 7.1 Assessment Elements with a full octet have which configuration? A.ionic configuration B.halogen configuration C.noble gas configuration D.transition metal configuration • A • B • C • D

49. Section 7-2 Section 7.2 Ionic Bonds and Ionic Compounds • Describethe formation of ionic bonds and the structure of ionic compounds. • Generalizeabout the strength of ionic bonds based on the physical properties of ionic compounds. • Categorizeionic bond formation as exothermic or endothermic. compound:a chemical combination of two or more different elements

50. Section 7-2 Section 7.2 Ionic Bonds and Ionic Compounds (cont.) ionic bond ionic compound crystal lattice electrolyte lattice energy Oppositely charged ions attract each other, forming electrically neutral ionic compounds.