CHEM 261 1st Edition Lecture 3Outline of Last Lecture:I. Atomic BondingII. Chemical Bonding Theory: Valence Bond TheoryIII. Bond TrendsIV. Hybrid Orbitals V. Structural RepresentationOutline of Current Lecture:I. Recap of Hybrid OrbitalsII. Electronegativity and Polar Covalent BondsRecap of Hybrid Orbitals:Things to remember about hybrid orbitals…1. # of orbitalssppp (sp3)= 4 orbitals!2. ExponentSp3 (3) = # of p orbitals involved in the hybridization3. Look at the bond, look at the hybrid (can go both ways!)Electronegativity and Polar Covalent Bonds:Covalent bond: 2 electrons share equally. Similar electronegativity between atoms - Polar covalent: electrons shared, but unequal attraction (partial +, partial -). Modest difference in electronegativity between atoms. Ionic Bond: electron transfer, held by electrostatic interactions. BIG difference in electronegativity between atoms.Electronegativity:-Electronegativity values: scale is arbitrary Periodic trend: Electronegativity increases left to right, top to bottom + electronegative: wants electrons, doesn’t give them up“-“ electronegative: give away electronsInductive effect- bond polarity contributes to unequal sharing of electronsDipole moment- The net dipole of a molecule. Electron pairs contribute to the partial negative character of a molecule. Absence of dipole moment? Net dipole moment = 0 (partial charges are equal, cancel each other
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