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CHM 2200 Exam #1 Study Guide CH 1-13I. Review of Gen ChemA. Covalent Bonds 1. Covalent Bond: formed by the sharing(usually involved when singly occupied valence orbital overlaps another) of electrons between atoms instead of complete transfer of electrons from one atom to the other.(1) Share 2 electrons= single bond(2) Share 4= double(3) Share 6= triple(4) If “unequal” sharing=> polar covalent2. General Rule: a atom shares enough electrons to reach a noble gas configurationa) For example- Hydrogen has 1 covalent to fill 1s^2b) Carbon in 4A needs four covalent bondc) See picture below ***Image 1A***3.4. If an atom loses one or more electrons becomes + charged called cation5. If atom gains 1 or more electrons it comes anionB. Covalent vs. Coordinate Covalent Bond1. Covalent: shared electrons from different atoms, bond is result of the overlap of 2 slightly filled orbitals (***think half and half) (so electrons come from both atoms.)2. Coordinate Covalent: bond that is formed by the overlap of a filled orbital with a vacant orbital on other atom. So both electrons come from the same atom.3. See picture below ***Image 2A***4.C. Drawing Lewis Structures (simple steps)1. Step 1) Find Total # Valence Electrons(1) Depending on which group see image 1A(2) Ex: PCl3 Phosphorus Group 5A= 5 valence and Cl 7A= 7 valence(3) 5+(3x7)= total 26 electrons2. Step 2) Find # to make “happy” (aka fill outer electron shell)(1) Elements up to period 4 on the periodic table need 8 electrons called octet rule.3. Step 3) Determine # of Bonds(1) Step 2 tells how many electrons needed and step 1 how many have. Subtract step 1 from the number in step 2 gives # of electrons needed to complete octet (remember each bond needs 2 electrons)(2) (Step2-Step1)/24. Step 4) Choose Central Atom (that is the least electronegative one or with highest valence)(1) Recall central atom up to 4 other atoms connected5. Step 5) Draw Skeletal Structure(1) Use straight line to represent bond 6. Step 6) Place Electrons around outside atoms(1) Complete octets around outside atoms if not enough electrons than structure from Step 5 if not enough step 5 wrong7. Step 7) Place remaining electrons around central atom(1) Complete octet for central atom with remaining electrons any bonds left from step 3 make double bonds(2) SEE THIS VIDEO FOR HELP!(3) http://www.youtube.com/watch?v=8JsK6rPpi70D. VSEPR Valence Shell Electron Pair Repulsion(1) molecules have specific shape that depend on number of electron bonds and lone pairs.(2) Atoms with 2 electron charge clouds= linear geometry 180 degrees(3) Atom with 3 charge clouds= planar triangular geometry 120 degrees(4) Atom with 4 charge= tetrahedral geometry 109.5 degrees(5) ***Image 3A***(6)E. Polar Covalent Bonds Review(1) Bonds are polar covalent if the bonding electrons are not shared equally between the atoms.(2) The ability to attract electrons in covalent bonds is electronegativity; highest upper right of periodic table and lowest lower left.(3) ***word of caution be aware of just because molecule has polar covalent does not make it polar see differences in picture below Water is polar versus CO2 not!(4) ***Image 4A***(5)(6) ***Image 7 A***II. Chapter 12 AlkanesA. Why is Carbon so “Special”?(1) Carbon is Tetravalent: it always forms 4 bonds(2) Abundant rich chemistry lots of different compound combinations etc.(3) Can make single, double, or triple bonds (can form strong Pi Bonds)(4) Create stable diverse structures: instead of inorganic compounds such as NaCl which has a high melting and boiling points because high number of oppositely charged molecules create very strong attraction. Organic molecules are joined by covalent bonds which are weak non-ioinic bonds they have a relatively low melting and boiling point. (leads to them being liquid at room temp)(5) Also organic compounds are usually insoluble in water and can have important consequences such as oil spills etc.B. Functional Groups(1) 18 million organic molecules been described with unique properties etc. We can understand them according to their structural features that the chemical behavior is often predictable based on specific grouping. These specific groups are called functional groups.(2) Functional group: an atom or group of atoms that has a characteristic physical and chemical properties. And are a part of a larger molecule.(3) THE CHEMISTRY OF ORGANIC MOLECULES MOSTLYDETERMINED BY ITS FUNCTIONAL GROUPS NOT ITS SIZE OR COMPLEXITY!(4) First 4 are Hydrocarbons - consist only of carbon and hydrogen bonds [alkane, alkene, alkyne, aromatic](5) Next 4 contain only SINGLE bonds and have carbon bonded to an electronegative atom (ex: Cl, F, Br, I, O, or N)(a) C-halogen= Alkyl Halide(b) C-Oxygen= alcohol(c) Two C-Oxygen(single bonds to each)= Ether(d) C- Nitrogen= Amine(6) The last remaining functional groups contain carbon oxygen DOUBLE BONDS(a) ALDYHYDE(b) KETONE(c) CARBOXYLIC ACID(d) ESTER(e) ANHYDRIDE(f) AMIDE (basically only C=O with a N on molecule)C. General Formula Cn H2n+2 (1) N=# of carbons(2) Ex: n=3(3) C3H(2x3)+2=C3H8D. Classifying Carbons as Primary(1), Secondary(2), Teteriary(attached to 4), Quaternary (5) is based on how many other carbons the carbon in question is connected to. See ***Image 1B*** BELOWE.F. Compounds with the same molecular formula, but different structural formulas are called ISOMERS(1) Example see picture below different ISOMERS of C5H12(2) ***Image 8A***(3)G. Image above has 3 constitutional isomers- are compounds with the same molecular formula but with different connections among their atoms.(a) Also notice the branched and unbranched alkanes above.(b) Constitutional isomers have DIFFERENT STRUCTURES, PHYSICAL PROPERTIES(melting and boiling points)H. EASY SUMMARY OF LEWIS, STRUCTURAL, LINE, AND CONDENSED WAY OF DRAWING COMPOUNDS. See formal charge explanation@ end of guide!I. Conformation- the specific 3 dimensional arrangement of atoms in a moleculeJ. Here we see CONFORMERS-which are molecular structures having idenical connections between atomsK. How to tell between Conformers and Isomers!!!!!(1) Simply name the 2 compounds using IUPAC (which will be explained next!)(2) IF THEY HAVE THE SAME NAME THEY ARE CONFORMERS IF THEY HAVE DIFFERENT NAMES, BUT THE SAME FORMULA THEY ARE ISOMERSL. How to Name(Nomenclature) Compounds?!?***Image 9A***(1) Step 1) Name the Longest Chain (see image 8A above!)(2) Step 2) Number the Chain of Carbons so that the lowest number near “branched


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FSU CHM 2200 - Exam #1 Study Guide

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