chapter9 - Electron Dot Structures & Valence Electrons...

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1 Electron Dot Structures & Chemical Bonding Chapter 8 Electron Dot Structures & Valence Electrons ¾ Electron Dot Structures – also known as Lewis dot structures – represent the valence electrons of atoms and show how they bond. ¾ Valence electrons are the outermost electrons of an atom that participate in chemical reactions. ¾ The outermost s and p electrons and electrons in unfilled d and f sublevels are considered valence electrons. ¾ We will primarily concern ourselves with main group elements, so we will usually consider only the s and p electrons. Bonding ¾ Ionic bonding ¾ Metal with nonmetal or polyatomic: z electron transfer and ionic bonding. z Each atom takes on a noble gas configuration (if possible). z Remember, some transition metals can make “noble gas like” (wanna be’s) by slight changes (like copper, iron) Ionic Compounds ¾ Ionic Compounds – Atoms form ions in order to achieve an OCTET – 8 valence electrons. ¾ Metal + nonmetal or polyatomic ¾ Electrostatic charge must balance Covalent bonding ¾ Nonmetal with nonmetal: z electron sharing and covalent bonding. z Electrons are held tightly and the atoms are still attractive to seek electrons. z This attraction pulls the atoms together to share. z (remember that some share more equally than others or “some animals are more equal than others (Animal Farm)) z Between the extremes (ionic vs covalent): Electronegativity and bond polarity Electronegativity ¾ Linus Pauling created an arbitrary scale to reflect how much an atom wanted an electron (check out history of Linus Pauling=interesting scientist; ¾ Fluorine really wants to acquire electrons=40 Fluorine really wants to acquire electrons 4.0 ¾ Cesium want’s to give up it’s electron = .7 ¾ Every other atom is somewhere between. ¾ It’s a very useful chart.
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2 Note: “Noble metals” at 2.2-2.4 = not reactive. 1A metal =very reactive, at .7 to .9. Metalloids = 2.0-2.2, nonmetals = 2.1 or higher. Metal with metal bonding: ¾ Metal atoms are large and the valence electrons are far from the nucleus. T z Electrons are not held tightly. z The metal atoms “pool” the valence electrons into an evenly distributed “sea” of electrons that “flows” between and around the metal ion cores. z The electrons are “delocalized”. z All metals are not the same. Some share electrons better than others. Best conductivity is in the gold area. Gold is not reactive and shares electrons easily, making a very conductive metal. Lewis Dot Structures ¾ Starting Point for understanding covalent structures and bonding. ¾ It’s a tool. We use it because it works. Element Electron Dot Structures ¾ Electron Dot Structures of atoms assume that s and p orbitals have the same energy (because of hybridization).
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This note was uploaded on 03/18/2010 for the course CHEM 210 taught by Professor Mcomber during the Spring '10 term at Skyline College.

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chapter9 - Electron Dot Structures & Valence Electrons...

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