Preview Homework due before every class period by 9 AM!-First LearnSmarts are due a week from today!-Purchase McGraw Hill Connect Code to access homework !Chapter Homework due one week after the chapter is finished!!!!!1.1 Atoms, Electrons & Orbitals (gen. chem. review)!!Atomic Number (2) - number of protons !Electrons (e-) - negative portion of the atom. Electrons are the ones that do chemistry. !Orbitals - where the electrons are located within the atom!-Quantum Numbers (helps locate electrons within the atom)!*Principle (n)- how far (energy level)!*angular momentum (l)- shape of the orbital !*magnetic quantum (m2)- 3D orientation !*spin (ms)- positive or negative spin!-Pauli Exclusion Principle: no two electrons will have the same four quantum numbers in an atom (individual locations)!Shapes of orbitals: !!!!!-Valence Electrons - outer electrons!-Isoelectronic- same number of electrons!"Octet Rule" - Noble gas configuration- WANT 8!!!*Builds compounds!*One type of bond!!IONIC vs. COVALENT!*Charged *Share!*Steal electrons!!-Cations!Na +!!Ionization Energy-!!-Anions!!e- + Cl (g) --> Cl- (g)!!Electron Affinity-!Ionic bonds formed -!Na+ + Cl- --> NaCl!!-How is it so stable??!+ strength of charge!-used mostly in inorganic compounds, so what is plan B?!!1.3 Covalent Bonding!"shared model"!!LEWIS STRUCTURES- 2D model of a molecule!-Shared electrons: - (dashed line)!-Unshared electrons: : (dots, one atom)!!!Examples:! draw methane (CH4) ethyl bromide (C2H5Br)!8e- !! !!!!!What happens if the octet rule isn't achieved?!-Double/ Triple Bonds!!1.4 Double/Triple Bonds!Prime Examples: Ethylene (C2H4)!!!!!!!Double bond- 4e- shared between 2 atoms!Triple bond- 6e-!!Examples: !Formaldehyde (CH2O) Hydrogen cyanide (HCN)!!!!!!!!!!!!1.5 Polar Bonding!Are electrons shared equally? NO!!Electronegativity: !!Representation of bond polarity: !!DELTA NOTATION vs. ARROW NOTATION!!!!!!One other way: electrostatic potential map!-Rainbow colors to show charge distribution!* BLUE show positively-charged ends while!* RED show negatively-charged sides!!Trends of electronegativity/ polarity!-Periodic table ! !!!!-Dipole moments!X -- Y 1. Strength!2. Bond length !!Indicate the direction of dipole moment!!!!!!!*Size and direction of dipole can hint at reaction types!!When species have charges (NH4+), is the charge on one atom?!!Formal Charge: !Book Formula: Group number - electron count!FC= 1/2 (shared) + unshared!Electron count= 8e- (N--> 4, H --> 1)!Dr. C "easy formula"!FC = what you start - what you get!5 - 4 = +1!*Charges of individual atoms MUST equal overall charge of the compound (if compound is +1, -1, etc., atoms must add to that)!!Realization of formal charge:!Electrons move --> delocalization!Reason for formal charge:!Electron bookkeeping (Don't lose electrons!)!!1.7 Structural Formulas!-more complex the larger they get!-more connections and more variety!-need a system:!!Example: C2H7N (many variations)!1. Determine molecular formula!2. Count valence electrons!20e-!3. Connect all bonded atoms using dashes (-) for a shared electron!!!!!!!!!4. Count all used electrons and subtract from total count!5a. Add electrons until atoms have 8e- around them (octet rule) or run out!5b. If one or more atoms has fewer than 8e-, use unshared electrons pari to form double or triple bonds!6. Calculate formal charges --> more stable (better)!!What if the same molecular formula give different structure?? Isomers!Two types: constitutional (structural) - different connectivity!stereoisomers - CH.7!!When does formal charge determine structures?!!Example: methyl nitrate CH3NO2!!Number of electrons: 24!!!!!!Rules for formal charges:!1. Smaller charges are better (O is most stable for most organics)!2. Adjacent atoms prefer opposite charges while destabilized by similar charges!3. Negative formal charges preferred location: electronegative atoms !!1.8 Resonance!What happens if we can draw more than one structure for a molecule?!!Example: carbonate ion (CO32-)!!!!!!!Proof that all three structures contribute to the experimental results?!-All bonds are same length !!*Resonance- two or more Lewis structures the differ by !Resonance hybrid: true structure of the various structures!!Resonance's role on electrons:!localized: shared between two atoms or unshared lone pair!delocalized: free flowing electrons!!--> easiest way to show delocalization (curve arrow system)! !!!!Are all resonance structures equivalent?!!GENERAL RULES OF RESONANCE:!1. Connectivity must be the same !-no atom movement; only electrons!2. Structures must have the same number of electrons and the same net charge!-formal charge on atoms may vary!3. Must have same number of unpaired electrons (no radicals made)!4.Don't break Octet rule (10 e- is not allowed)!!!!!!!!!!Resonance Contributions!1. The greater number of shared (covalent) bonds contributes more to stability (Don't violate Octet rule!)!2. Little separation of charged!No same charges!!3.Negative formal charges on electronegative atoms!O-, Cl-, F-, N!!1.9 Writing Organic Structures!!-Chemists are lazy!- Many differ representations that highlights different things!!!CH3CH2OCH2CH3 (condensed formula)!!!!Condensed formulas- leave out many of the covalent bonds, lone pairs, and use subscripts for identical groups attached to atoms!!Examples: CH3CHCl2!!Condensed is good... but we can get lazier and draw structures faster!Bond-line formula (skeleton structures) -!!CH3CH2CH2CH3 --> !!!!!!!1. Carbon at every vertx (unless noted otherwise) or at the end of the line!2. Hydrogens are typically omitted!3. When atom is neither C or H, it is shown with necessary H atoms (heteroatom)!!Examples:!Expand this structure - (show all atoms)!!!!!!!!!!!!1.10 Shapes of Molecules!Review of molecular geometry for gen. chem.!!CH4 (methane) H2O (water)!!!!!!!!!!Valence shell electron-pair repulsion model - VESPR model!-Unshared electrons dominate!-Electrons want to get away from each other!-Multiple bonds (double and triple) are treated as one unit !-Useful prediction for geometry but not perfect!!1.11 Molecular Dipole Moments!-Combination of molecular geometry and bond polarity!!Is carbon dioxide polar?!Both bonds are polar! But molecular is not polar!!!!What about chloromethane (CH3Cl)?!!!!!!!!!1.12
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