1. 1 Chemistry 111 Sections 11.1 – 11.8 Chemistry 111

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3. 3 Outline Recap of Chapter 10 –Quantum Mechanics Rules –Valence Electrons & Noble Gas Configuration Chapter 11.1 – 11.7: –Chemical Bonding with Ionic & Covalent compounds.

4. 4 Quantization – A Concept. Quantum means that a property (e.g. electron’s energy, altitude in the classroom) can only have certain values. Example: –going up stairs (is)/(is not) quantized –going up a ramp is (is)/(is not) quantized. –length of string is (is)/(is not) quantized –amount of flour in cookies (is)/(is not) quantized –number of eggs (is)/(is not) quantized

5. 5 Quantum Mechanics Steps I have a 6-step program to review quantum mechanics rules. Step #1: Keep “n” from the Bohr Model –Quantum Mechanics refines Bohr’s Model –“n” is the “Principle Quantum Number” –Matches row number on the periodic table.

6. 6 Quantum Mechanics Steps Step #2: Add “sublevels” –s sublevels are spherical –p sublevels are pear shaped (2 flower petals) –d sublevels are mostly 4-petal flowers –f sublevels are mostly 8-petal flower sp df

7. 7 Quantum Mechanics Steps Step #3: Add “orbitals” Sublevel# of Orbitals s1 p3 d5 f7

8. 8 Quantum Mechanics Steps Step #4: Electron Capacity, 2 e – per orbital Sublevel# of Orbitalse - Capacity s1 1  2= 2 p3 3  2= 6 d5 5  2= 10 f7 7  2= 14

9. 9 Quantum Mechanics Steps Step #5: Energy level e – capacity. n# SublevelsNamese – Capacity 11s 1  2= 2 32s, p 1  2= 2 +3  2= 6 8 53s, p, d 1  2= 2 3  2 = 6 +5  2= 10 18 74s, p, d f … = 32

10. 10 Quantum Mechanics Steps Step #6: Orbital Filling / Building an Atom –Recipe for an atom: Choose Element, add protons & neutrons Add electrons into orbitals until # e – = #p –Filling Order: Start at lowest energy level Start at lowest suborbital Add electrons 1 at a time, remember to “use all empty seats on the bus” –Be capable of drawing the energy level diagram –Write the electron configuration (1s 2 2s 2 2p 6 3s 2 …)

11. 11 Valence Electrons Defined as electrons in outer shell –We will mostly work with “s” & “p” electrons How many valence electrons in a neutral atom? –Column number on periodic table. I A = 1 valence e – II A = 2 valence e – VI A = 6 valence e – VIII A = 8 valence e –

12. 12 Noble Gas Electron Configuration Noble gases are special: –They have full outer shells. –Both s & p sublevels are full. –They don’t want to react / bond with other atoms Everyone wants to be like a noble gas: –Atoms form ions to get a full outer shell. –Atoms share electrons to get a full outer shell. As we learned last time, the noble gas electron configuration is: ns 2 np 6

13. 13 Periodic Trends – Atomic Radii

14. 14 Periodic Trends – Ionization Energy

15. 15 Chapter 11: Chemical Bonds Chapter 11 Topics –Monatomic (1 atom) Ions –Ionic Bonds –Covalent Bonds –Covalent Bond Polarity –Multiple (double/triple) Bonds –Simple Molecules –Metal Bonds What we’ll do: –Discuss Ions –Ionic Bond Movie –Covalent Bonds –Examples of Covalent Bonds –Polarity

16. 16 Ions We use the periodic table to predict what ions an element forms. Noble Gas Configuration: –Elements ionize to get a full or empty outer shell (which ever is faster) Column Numbers –Use the IA – VIIIA columns. IA (1A) =1+VIIA (7A)=1- IIA (2A) = 2+VIA (6A)=2- IIIA (3A) = 3+VA (5A)=3- IVA (4A) = ? –Ignore Transition Metals for now. Examples: Na, Al, Se, As, Ba, Sb, I, Xe

17. 17 Movie Movie on ionization: 2 Na (s) + Cl 2 (g)  2 NaCl (s)

18. 18 Covalent Bonds Recall from Previous Chemistry Class: –Ionic = Electrons Transferred, Covalent = Electrons shared. –Lewis Diagrams Use: Elemental Symbols (1 for each atom in the molecule) Dots Represent Electrons (usually paired) Lines Represent Bonds (2 electrons per line) –Things bond until they get 8 valence electrons (except Hydrogen) Each atom take credit for all electrons in its bonds.

19. 19 Lewis Diagram Each H counts 2 e - Fluorines each count: LP 2  3=6 8 e - BP 2  1=2 Oxygens each count: LP 2  2=4 8 e - BP 2  2=4 NH 3 HH FF OO NH H H

20. 20 Big, Ugly Lewis Diagram H gets 2 e -, C, N & O each get 8 e - C C C C C C H O H H H N H H H O

21. 21 Exceptions Sometimes we can’t make everything work – and the octet rule gets broken. –Not enough Electrons These “radicals” are quite reactive / Toxic NO NOO

22. 22 Bond Polarity Covalent Bonds involve Sharing Electrons but not all Sharing is equal! Hydrogen Fluoride is a good example. –Fluorine is grabby and pulls electrons to it. –Hydrogen isn’t as grabby and loses its electrons We can use “Electronegativity” to decide.

23. 23 Electronegativity Table H 2.1 He Li 1.0 Be 1.5 B 2.0 C 2.5 N 3.0 O 3.5 F 4.0 Ne Na 0.9 Mg 1.2 Al 1.5 Si 1.8 P 2.1 S 2.5 Cl 3.0 Ar K 0.8 Ca 1.0 Ga 1.8 Ge 1.8 As 2.0 Se 2.4 Br 2.8 Xe

24. 24 Using Electronegativity (EN) 1.Look up the EN values for each Element: H = 2.1, F = 4.0 2.Compute the difference (make it >0)  EN = 4.0 – 2.1 = 1.9 3.Rate the difference: 1.7Probably Ionic Note: Hydrogen cannot form Ionic Bonds!

25. 25 Who cares about Polarity? Polar molecules (e.g. H 2 O) dissolve other polar molecules. Polarity governs the TLC lab. Extreme Polarity holds DNA together. Polarity governs how proteins fold. Mayonnaise depends on polarity…