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Let’s review

Let’s review. O 8 8 8 1s 2 2s 2 2p 4. Oxygen Symbol? Atomic Number? Protons? Electrons? Electron Distribution?. Oxygen has 6 valence electrons. Episode 502. Electron Dot Diagrams. Atom’s symbol surrounded by dots to represent its valence electrons. Example Oxygen

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Let’s review

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  1. Let’s review • O • 8 • 8 • 8 • 1s2 2s2 2p4 • Oxygen • Symbol? • Atomic Number? • Protons? • Electrons? • Electron Distribution? • Oxygen has 6 valence electrons. Episode 502

  2. Electron Dot Diagrams • Atom’s symbol surrounded by dots to represent its valence electrons • Example • Oxygen • 6 valence electrons • Lithium • 1 valence electron Episode 502

  3. Problem Set 1 Draw the Electron Dot Diagrams for: Magnesium Helium Krypton Aluminum Bromine Potassium Nitrogen Silicon Strontium Episode 502

  4. Lewis Structure • Diagram representing the arrangement of valence electrons in a molecule • Most atoms need 8 valence electrons to become stable. The exceptions are H and He which need 2 valence electrons to be stable. Episode 502

  5. Lewis Structure for H2 • 2 electrons belonging to both atoms • Represented by a dash between the symbols • H - H • Shared pair Episode 502

  6. Lewis Structure for Cl2 • Each Cl atom has 7 valence electrons; giving a total of 14 valence electrons to work with. • Shared pair • Unshared pair • Electrons belonging to only one atom • Represented by 2 dots Episode 502

  7. Lewis Structure for HCl H - Cl Episode 502

  8. When more than two atoms bond, you must determine which is central. • The central atom is: • Frequently carbon • Never hydrogen • Often atom with the smallestelectronegativity H • Lewis structure for CH3I • (Thereare a total of 14 valence electrons to work with.) H C I H Episode 502

  9. Problem Set 2 NH3 CH2Cl2 CH3OH (a little tricky) C6H12 (Hint: The carbon atoms form a ring.) Episode 502

  10. Lewis structure of ethene, C2H4 • (has total of 12 valence electrons) H H C C H H Single bond 1 Double bond 2 Triple bond 3 Episode 502

  11. Problem Set 3 CO2 HCN CH2O C2HCl Episode 502

  12. Polyatomic Ion • Covalently bonded groups of ions with a charge NO3-1 Has gained 1 electron to give a total of 24 valence electrons to work with • N = 5 electrons • O = 3 x 6electrons = 18 electrons • -1 = 1 extra electron • [ ]-1 O N O O Episode 502

  13. Problem Set 4 PO4-3 SO4-2 NH4+1 CN-1 Episode 502

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