CHEM 251 1st Edition Lecture 11 Outline of Last Lecture I. Clicker QuestionsII. Group ProblemIII. ApplicationsIV. Hydrogen EconomyOutline of Current Lecture V. Clicker QuestionVI. MetalsVII. Band TheoryVIII. PropertiesIX. Band GapCurrent LectureX. Clicker Questiona. Answer: Conduction BandXI. Metalsa. What are metals? 3-D electrical conductivity at SATPb. Conductive, reflective, shiny, malleable or ductile, high melting pointsc. Bonding from molecules to materialsi. Lithium: becomes Li4, ½ band = empty conduction band, other ½ = filled valence bandii. Beryllium: filled conduction band and valence band, so doesn’t seem like it would form metallic structures1. BUT-mixing w/ p-orbitals unlocks conduction bandThese 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.iii. Sodium: half filled because of its electron configuration so no mixing needed vs. magnesium, where s-p mixing is importantXII. Band Theorya. Conductive metals can easily access antibonding orbitalsb. Always energetic price to pay for this but the heat from room temp is enoughXIII. Propertiesa. Bonding occurs through s orbitals so angles are not importantb. Explains ductility or malleabilityc. Flexible bonds but STRONG, explains high melting pointsi. Exceptions- liquid metals at room tempd. Metal reactivityi. More reactive down a groupii. React w/ water so only a few metals are found in nature in their elemental formXIV. Band Gapa.b. Siliconi. Semiconductorii. Poorly conductive under normal conditionsiii. Highly conductive under lightiv. Electrochemical bias potential can be appliedv. Doping 1. B-doped (p-type) *accepts electronsa. Low-lying B orbital filled leaves hole in valence band2. P-doped (n-type) *donates electronsa. High-lying P orbital promotes electron to conduction bandb. Electron transport in conduction band is mode of
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