chem001-chapter05-notes

chem001-chapter05-notes - CHEM 001 Lecture Notes, Prof....

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CHEM 001 Lecture Notes, Prof. Wei-Min Dai 33 Chapter 5 Chemical Bonds: The Ties That Bind Chemical Bonds • Forces responsible for holding together atoms in molecules and ions in crystals • Determine shape of molecules • Predict chemical and physical properties of materials • Related to arrangement of electrons in compounds Stable Electron Configurations • Valence electrons – outermost level with electrons • Core electrons – all other electrons in an atom • Isoelectronic – same number of valence electrons Lewis (Electron-Dot) Structures • Valence electrons represented by dots • Lewis symbols – Examples: Na•, •Mg•, … Lewis
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CHEM 001 Lecture Notes, Prof. Wei-Min Dai 34 Lewis Structures for Ions • Add electrons for anions Cl • Remove electrons for cations Na + Sodium Reacts with Chlorine • Sodium dropped in flask filled with chlorine gas – Produces sodium chloride (i.e., table salt) • Chlorine extracts electron from sodium Ionic Bonds •N a + and Cl • Opposite charges attract • Ions organize themselves in orderly manner –Crys ta l of NaC l More Ionic Compounds See more on this reaction at http://en.wikipedia.org/wiki/Magnesium_nitride [Mg 3 N 2 ]
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CHEM 001 Lecture Notes, Prof. Wei-Min Dai 35 Octet Rule • Atoms tend to gain or lose electrons to have eight valence electrons – Same as noble gases – He and H are exceptions, get only two valence electrons Naming Ions • For cations, simple positive ions – Add the word ion –Examp les : Na + – sodium ion Al 3+ – aluminum ion • For anions, simple negative ions – Change the usual ending to - ide : C l
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This note was uploaded on 02/14/2012 for the course CHEM 001 taught by Professor Wei-mindai during the Fall '08 term at HKUST.

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chem001-chapter05-notes - CHEM 001 Lecture Notes, Prof....

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