chp7_slides - CHP. 7 CHEMICAL FORMULAS and BONDING Overview...

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CHP. 7 CHEMICAL FORMULAS and BONDING Overview of Types of Bonds Ionic Bonding: forms ionic compounds. 1. electrons are transferred from one atom to an- other. 2. resulting cation (+) and anion (-) form a strong bond. 3. Electronegativity Difference is greater than 1.7 (New York State Regents criterion) 4. Ionic Compounds: (a) have high melting points. (b) are brittle, cleave along planes. (c) are composed of ions (not atoms): they con- duct electricity when dissolved or molten; the current is carried by their charged ions.
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Covalent Bonding 1. is a sharing of electrons between two atoms. 2. causes atomic orbitals to overlap and deform since the electron distribution is changed from the atomic situation. 3. results in a lowering of potential energy from the situation in which the two atoms are isolated. 4. nucleus of each atom attracts the other atom’s valence electrons to the extent that the electrons are associated with both atoms.
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Metallic Bonding 1. Nuclei and core electrons are arranged in an or- derly network (crystal). 2. Network is immersed in a sea of valence elec- trons which holds the network together. These electrons are said to be delocalized through a metallic compound. 3. The more valence electrons in the electron sea, the more tightly bound are the atoms in the network. e.g.: i. Sodium, with few valence e - is easily deformed (atoms can slide over each other easily). ii. Iron, with more valence e - , is not. 4. Metallic compounds are considered to be made up of atoms (not ions) since the neutralizing electron sea is associated with all of the sites (nuclei + core e - ) equally. Note: The term electron sea is the actual terminology used by scientists to describe this electronic structure.
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The Octet Rule Atoms will gain, lose, or share electrons to gain a ”complete set” of valence electrons. Q: What is a ”complete set”? A: Filled ns and np sublevels (i.e.: ns 2 np 6 ) Q: Why? A: Because the next electron to go in starts a
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This note was uploaded on 10/19/2011 for the course PHY 2020 taught by Professor Staff during the Spring '08 term at University of Florida.

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chp7_slides - CHP. 7 CHEMICAL FORMULAS and BONDING Overview...

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