Exam # 1 Study Guide Chapter 1-3Organic Chemistry Test #1 Study GuideChapter 1 Lectures 1-21.1 How Electrons are Arranged in AtomsAtoms: Contain a small dense nucleus, surrounded by electronsNucleus: Positively charged, contains most of the mass of the atom-Consists of Protons and Neutrons-Exception = Hydrogen, whose nucleus consists of a single protonProtons: Positively chargedNeutrons: Neutral chargeAtomic Number: Equal to the number of protons in it’s nucleus-And to the number of of electrons around the nucleus in a neutral atomAtomic Weight: Equal to the sum of the number of protons and the number of neutrons in the nucleus. We don’t count the electrons because they are very light by comparisonOrbitals: Where electrons are located. They are grouped in shells, and can hold a maxi-mum of 2 electronsValence Electrons: Located on the most outermost shell. The kernal of the atom con-tains the nucleus and the inner electronsS- 1 OrbitalP- 3 OrbitalsD- 5 Orbital CHEM 2030 *The greater the atomic number, the greater the number of electrons...1.2 Ionic and Covalent BondingInert Gas: Has a stable electron configuration-Does not combine with other atomsIonic Bonds: Composed of positively charged cations and negitively charged anionsElectropositive: Atoms give up electrons and form cationsElectronegative: Atoms accept electrons and form anions*Generally speaking, the more electropositive elements when looking at the peri-odic table, are farthest to the right and higher up. Atoms are more electropositive when it is easier to lose an electonEx: Li3+ is more electropositive than Be4+Ex: Na2+ is more electropositive than Li2+ because it is shielded energy by 2 in-ner shells. Therefore it is less energy for Na2+Covalent Bond: Formed when two atoms share one of more electron pairs.Molecule: Consists of two ore more atoms joined by covalent bondsEqual Electronegativities: The electron pairs are shared equallyBond Energy (BE): The energy necessary to break a mole of covalent bonds. The amount of energy depends on the type of bond broken.H-H bond = Very strongBond Length: Average distance between two covalently charge atoms1.3 Carbon and the Covalent BondWe allow the letter C stand for the KernelC has 4 valence electrons, and therefore carbon’s valence shell is half filledTherefore it is neither strongly electropositive or electronegative; in the middleIt usually forms covalent bonds, like CH4, to complete their valence shells1.4 Carbon-Carbon single bondRadical: A molecular fragment with an odd number of unshared electrons. In the Carbon-Carbon bind, each carbon is attached to a carbon and 3 Hydrogen's, or 3 chlorine atomsCatenation: The ability of an element to form chains of its own atoms through covalent bonding1.5 Polar Covalent BondsA covalent bond in which the electron pair is not shared equally between the two atomsEx: HCl, the arrow is towards the Cl (Delta -)“delta plus and delta minus”Ex: Tetrachloromethane, Chlorine is more electronegative than Carbon. The elec-trons for each C-Cl bond are therefore displaced toward the Cl-C= Delta +-Cl = Delta -1.6 Multiple Covalent BondsDouble Bond: Two electron pairs are shared between 2 atomsNonbonding Electrons: Unshared electron pairs, reside on one atomTriple Bond: Three electron pairs are shared between 2 atomsEx: H-C=-N (=- triple bond)Hydrocarbonds: Compuonds composed of just hydrogen and carbon atomsThere are multiple different forms this structure can have2 carbons per molecule# of Hydrogens changes what the atom is2 H = Athyne4 H = Ethene6 H = Ethane1.7 ValenceValence: Number of bonds that an atom of one element can form# is equal to the number of electrons needed to fill the valence shellH = 1, C = 4, N = 3, O = 2, F = 1, Cl = 11.8 IsomerismMolecular Formula: Gives the number of different atoms presentEx: H2OStructural Formula: Indicates how those atoms are arrangedEx: H-O-HIsomers: Molecules with the same number and kinds of atoms but different arrange-ments of the atoms“Same formula-Different Connectivity”Structural Isomers: Have the same molecular formula but different structural formulas 1.9 Writing Structural FormulasContinuous Chain: Atoms are bonded one after the otherEx: C-C-C-C-CBranched Chains: Some atoms form branches from the longest continuous chain1. Write down all atoms2. Add the correct number of valence electrons to each atom3. recignize electron lone pairs; write a dash4. Connect atomsa. At least one bondb. There might be more than one isomerc. Connect H atoms’ CH3, CH2, CH groupsd. Consider multiple bonds1.10 Abbreviated Structure FormulasSome formulas we write out take up a ot of space and get very comlicated, so we take shortcuts that will convey the meaning of structural formulas Ex: Ethyl Alcohol = CH3CH2OH*A complete Lewis Structure 1.11 Formal ChargeFormal Charge: Convalently bonded molecule or ion is the number of valence electrons in the neutral atom minus the number of covalent bonds to the atom and the number of unshared electrons to the atomHydronium Atom has actual overcharge of +1, Oxygen has a formal charge of +11.12 ResonanceResonance: Two or more structures with identical agreements of the atoms but different arrangements of the electronsResonance Hybrid: If resonance structures can be written, the true structure of the mol-ecule or ion is a resonance hybrid of the contributing resonance structureBoth forms are OK+Use corner brackets and put the charge on the outside top right corner1.13 Arrow FormalismUse a curved arrow: Moves and electron pairStarts ar the center of the existing pairEnds at the intended center of the pairA-B and make it A + B, both electrons go with BUse a curved arrow with half head: Use for Homolysis, to break up A-B and make it A + BOne electron goes with A and one electron goes with B1.14 The Orbital View of Bonding; The Sigma BondP + S --> p-s Sigma bondP + P --> p-p Sigma bondP + P (vertical) -> Pi Bond Carbon SP-3 Orbitals & Tetrahedral Carbon; The Bonding of MethaneSP = LinearSP2 = Trigonar Planar,0 lone e- = bent, 1 lone e- = trig planarSP3 = Tetrahedral 0 lone e- = tetra, 1 lone e- = trig pyramid, 2 lone e- = bentAKA:SP3 (geometrical shape) = tertrahedralSP2 (geometrical shape) = trigonal planarSP (geometrical shape) = linearTetrahedral (no lone pairs) = tetrahedralTetrahedral (one lone pair) = trigonal pyramidalTetrahedral (two lone pairs) = bentTrigonal Planar (one lone pair) = bentTrigonal Planar (no lone pairs) = trigonal planarExtra Chapter