Chem 1320 1st Edition Lecture 30Outline of Last Lecture I. Electronegativity II. Dipole Moment: PolyatomicsOutline of Current LectureI. Polar Covalent BondsII. Lewis Structures III. Procedure of Assigning Formal ChargesIV. BondsCurrent Lecture I. Polar Covalent BondsPolar bonds have more double bonds. A rule of thumb is that like dissolves like. Nonpolar solvents dissolve nonpolar molecules and polar solvents dissolve polar molecules. Nonpolar things are stored and only released using fats. Polar molecules stay in the body for less time andare easily lost in urine. II. Lewis StructuresWhen determining the central atom place one with the lowest electronegativity. Formal charge can be determined after drawing structures. It is possible to draw multiple correct Lewis structures. The basic principal of figuring out which way is best is by assigning atomic charges tothe atoms based on the atom sharing the electrons in the bond equally. We want to find a structure that minimizes the assigned charge. Charge assignment is different than oxidation numbers because they are purely the ionic model. III. Procedure of Assigning Formal ChargesElectrons in bonds you must count and divide. Then you assign half of the electrons in a bond toeach atom participating in the bond. The lone pairs of electrons need to be counted and stuck to the original atom it was found on. Formal charge is the number of valence electrons on the free element minus the total formal charge of a molecule is the sum of the atomic formal These notes represent a detailed interpretation of the professor’s lecture. GradeBuddy is best used as a supplement to your own notes, not as a substitute.charges. The best Lewis Structure is the one that minimizes the overall formal charge on each atom. A single Lewis Structure can sometimes be insufficient on find the formal charge. IV. BondsThere are single, double, and triple bonds. Resonance is the averaging of the possible structures. When we write Lewis Structures, use only the electrons, not the atoms when drawing the resonance. The more possible resonance structures are more stable
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