GENERAL CHEMISTRY 2 - CHEMICAL BONDING CHEMICAL BONDING WHY...

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CHEMICAL BONDING
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CHEMICAL BONDING WHY DO ATOMS BOND? WHAT IS OCTET RULE? -atoms tend to lose , gain or share electrons in order to achieve stable valence shell electron configuration of 8 electrons. TYPES OF CHEMICAL BONDS IONIC BOND COVALENT BOND
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LEWIS DOT SYMBOLS Symbol of the element with one dot for each valence electron Group no. of representative elements is equal to the number of valence electrons in its last shell. Na Ca Al C N O Cl Xe
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IONIC BONDING An ionic bond is the electrostatic force that holds positive and negative ions together. Draw the bonding of the following atoms 1. Barium and Phosphorus 2. Lithium and Oxygen 3. Calcium and Chlorine
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COVALENT BONDING A bond in which two or more electrons are shared by two atoms Idea of covalent bond was first suggested by Gilbert Newton Lewis in 1916.
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COVALENT BONDING Illustrate the bonding of the following atoms 1. Carbon and Hydrogen 2. Nitrogen and Hydrogen 3. Oxygen and Hydrogen
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COVALENT BONDING SINGLE BOND: Sharing of a single pair of electrons between bonded atoms . DOUBLE BOND: sharing of two pairs of electrons between two atoms ( O = O) TRIPLE BOND: sharing of three pairs of electrons between two atoms. (N N)
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TYPES OF COVALENT BONDING POLAR COVALENT BOND electrons are not equally shared NON POLAR COVALENT BOND equal sharing of electrons COORDINATE COVALENT BOND a single atom contributes both of the electron to a shared pair. (to be discussed in exceptions to octet rule)
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COMPARISON OF PROPERTIES OF COVALENT AND IONIC COMPOUNDS PROPERTIES IONIC COVALENT ATTRACTIVE FORCES Electrostatic forces between ions that are very strong Bond energy holds atoms together (intramolecular forces) Intermolecular forces are prevalent between molecules which are very weak OTHER PROPERTIES Very high melting pt. Conduct electricity as molten liquid Low melting point solids Do not conduct electricity Most are not soluble in water
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BOND POLARITY Recall that a polar bond has an asymmetric distribution of electrons X-X is nonpolar X-Y is polar Polarity of a bond increases with increasing difference in electronegativity between the two atoms Bond is a dipole One end is ( δ + ), while the other is ( δ - )
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Polarity - Molecules Molecules may also possess polarity Positive and negative poles Molecule is called a dipole Consider HF H is δ + while F is δ Consider BeF 2 Be-F bond is polar BeF 2 is nonpolar
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ELECTRONEGATIVITY SCALES PAULING SCALE relative scale used to measure electronegativity Atoms with vastly different electronegativity ionic compounds Atoms with somewhat different electronegativity polar covalent compound (approximate cut off is a difference of 2.0 on the Pauling Scale) Nonpolar compounds are electronically symmetrical
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Determine whether the given molecule is polar or nonpolar 1.SO 2 2.BF 3 3.CO 2
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This note was uploaded on 10/19/2011 for the course CHEM 12 taught by Professor Ma'amordono during the Summer '11 term at Mapúa Institute of Technology.

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GENERAL CHEMISTRY 2 - CHEMICAL BONDING CHEMICAL BONDING WHY...

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