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CHEM 222—Descriptive Inorganic

CHEM 222—Descriptive Inorganic. Welcome back from break…hope all was well Today’s coverage… Syllabus—news, notes, etc from the syllabus Course overview…again, sort of taken right from syllabus Lab—today…start at 2:00 p.m. won’t last full period Text—Rayner-Cahnam (4 th edition).

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CHEM 222—Descriptive Inorganic

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  1. CHEM 222—Descriptive Inorganic • Welcome back from break…hope all was well • Today’s coverage… • Syllabus—news, notes, etc from the syllabus • Course overview…again, sort of taken right from syllabus • Lab—today…start at 2:00 p.m. won’t last full period • Text—Rayner-Cahnam (4th edition).

  2. …Structural Inorganic… Stoichiometry/Yields/LR Molarity and dilution Common polyatomic ions Solubility rules Redox reactions Oxidized/Reduced Agents (ox and red) Atomic Orbitals, shapes/types Electron Configurations Periodic trends (AR, IR, IE, EN) Bonds…covalent to ionic Lewis Dot Structures (VSEPR) Polarity (& other intermolecular) MO Theory Solution Chemistry (calcs) Equilibrium Ksubscript where the Ksub = a, b, c, w, sp, p Titration calculations Titration curves (strong/weak acids and base titrations) Representative Chemistry What to expect when you’re expecting…

  3. A summary of simple periodic trends

  4. Determine the number of valence electrons • Draw a skeletal structure (takes practice…use table below) • Distribute excess electrons—make octet • Excess electrons go to central atom, deficiency—multiple • Calculate formal charge of each atom (table below helps)

  5. Oh, all right…I’ll go back to Organic • Not really going to drag this out much, you ALL should know this pretty well • Methane, ammonia and water, the unholy trinity? • 4:0 tetrahedral • 3:1 trigonal pyramidal! • 2:2 bent (I hate ‘angular’) • Note bond angles!!

  6. Simple Solubility Guidelines

  7. Nomenclature—simple naming • Pretty scary looking table—not so bad if you note trends. • Consider phosphate, sulfate, nitrate, chlorate (parent) • Add an oxygen—add a ‘per’ • Lose an oxygen—’ate’ becomes ‘ite’ • Lose two oxygens—hypo ‘parent’ ite • ClOx series demonstrates this

  8. Formal Charge—Quick and Dirty • Books give a formula for calculating formal charge, but those are pretty clunky…something simpler • Count all bonds (as 1) and lone pair electrons (1 for each electron) • Btw…thiocyanate? Replace the O with an S O C N # valence e’s (for element) 6 4 5 Number e’s (see counting) 6 4 6 Subtract 2 from 1 0 0 -1 Formal Charge resides on Nitrogen Here, formal charge is on the oxygen. Are these resonance forms?

  9. Acid Base Chemistry • Probably should have learned this in General Chemistry, but alas…not so much. Time to recall • Equilibrium Ka, Kw…ring any bells? • Derive the Henderson Hasselbach equation • Use to calculate buffer solutions? • Instead of long drawn out lecture, perhaps best to do an AB review. Here, have a nice problem set.

  10. Alternative version of Slater • Still 4 rules…modified from last week • Write the electron configuration based on “n”. • Electrons to the right contribute nothing • For s, p orbitals • Other electrons in same ‘n’ group—0.35 • Electrons in lower (n-1) group—0.85 • Electrons in n – 2 group—shield fully 1.00 • For d, f electrons • Other electrons in the (d or f) group—shield 0.35 • Everything else shields fully

  11. Atomic Radius (cov. radii) • Covalent radii • Note smooth trend (for the most part) • Slater for F, Cl? Do the quick calcs • Makes sense • Na, K?

  12. From Atomic Radius to IE • Zeff works well to explain AR—how about IE? • IE…defined as the energy needed to remove an electron • IE2 IE3 etc as the number of e’s removed increases. • Works “ok”, not perfect. • Why the break Be/B • N/O?? • K/Na?? • Again…Explanation!!!

  13. Last bits from Chapter 2 • Bertrand’s rule—some better than none, some better than too much. • Avoid the black.

  14. Brief overview of MO Theory • Hybridization of ATOMIC orbitals produces molecular orbitals (Organic should have drilled this into you) • Number of hybrid orbitals needed => number EG’s!! • That’s how EG is important…gives shape of molecule

  15. So what happens when MO’s overlap? • First of all, you’ll likely form a bond!! • Picture on right shows the interaction of two orbitals. • Sigma and pi • Lighter shade of green denotes a (-) sign of the mathematical equation that describes this region of space • + and – interactions for orbitals really unhappy (nonbonding)

  16. General Statements about MO • Signs of the wavefunctions must be the same • Two AO’s in…2 MO’s out. (bonding/antibonding *) • Good mixing comes from MO’s of similar energy • 1s mixes NOT with 4f… • MO’s have 2 e’s, spin up/spin down • Fill the MO’s the same way you fill AO’s for atoms • Maximum multipicity • Bond order? Number of bonding pairs – number anti

  17. Doing the dirt simple ones H2 He • s, orbitals called ‘sigma bonds’ • p, orbitals called pi bonds • What “makes” sigma or pi bonds… • This designation comes from symmetry (which we cover in more detail later).

  18. MO’s depicted in an Energy Diagram

  19. For the uber lazy…the summary panel

  20. Molecular symmetry • What IS symmetry? Sort of an abstract concept, but for chemistry, it’s a molecule with indistinguishable configurations • The operations that leave a molecule “looking the same” (indistinguishable) are called “symmetry operation”

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