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Unformatted text preview: Chapter 3 Structure and Properties of Ionic and Covalent Compounds Denniston Topping Caret 5 th Edition Edited by Ahmad Audi Edited by Ahmad Audi For CHEM1070 For CHEM1070 3.1 Chemical Bonding Chemical bond- the force of attraction between any two atoms in a compound This attractive force overcomes the repulsion of the positively charged nuclei of the two atoms participating in the bond Interactions involving valence electrons are responsible for the chemical bond 3.1 Chemical Bonding Lewis Symbols Lewis symbol (Lewis structure) - a way to represent atoms using the element symbol and valence electrons as dots As only valence electrons participate in bonding, this makes it much easier to work with the octet rule The number of dots used corresponds directly to the number of valence electrons located in the outermost shell of the atoms of the element 3.1 Chemical Bonding Lewis Symbols Each side of the symbol represents an atomic orbital, which may hold up to two electrons Using Lewis symbols Place one dot on each side until there are four dots around the symbol Now add a second dot to each side in turn The number of valence electrons limits the number of dots placed Each unpaired dot (unpaired electron of the valence shell) is available to form a chemical bond Lewis Dot Symbols for Representative Elements 3.1 Chemical Bonding 3.1 Chemical Bonding Principal Types of Chemical Bonds: Ionic and Covalent Ionic bond- a transfer of one or more electrons from one atom to another Forms attractions due to the opposite charges of the atoms Covalent bond- attractive force due to the sharing of electrons between atoms Some bonds have characteristics of both types and not easily identified as one or the other Ionic Bonding Representative elements form ions that obey the octet rule Ions of opposite charge attract each other creating the ionic bond When electrons are lost by a metal and electrons are gained by a nonmetal Each atom achieves a Noble Gas configuration 2 ions are formed; a cation and anion, which are attracted to each other 3.1 Chemical Bonding 3.1 Chemical Bonding Consider the formation of NaCl Na + Cl NaCl Sodium has a low ionization energy it readily loses this electron Na x Na + + e- When sodium loses the electron, it gains the Ne configuration Chlorine has a high electron affinity When chlorine gains an electron, it gains the Ar configuration o . : .. .. Cl : e .. .. Cl : Ionic Bonding 3.1 Chemical Bonding Essential Features of Ionic Bonding Atoms with low I.E. and low E.A. tend to form positive ions Atoms with high I.E. and high E.A. tend to form negative ions Ion formation takes place by electron transfer The ions are held together by the electrostatic force of the opposite charges Reactions between metals and nonmetals (representative elements) tend to be ionic Ion Arrangement in a Crystal As a sodium atom loses one electron, it becomes a...
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This note was uploaded on 06/04/2008 for the course CHEM 1070 taught by Professor Jenson during the Spring '08 term at Notre Dame OH.
- Spring '08