McF7S - Chemistry 107: General Chemistry Chemistry for...

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Chapter 7 1 Chemistry 107: General Chemistry Chemistry 107: General Chemistry for Engineers for Engineers Prof. Jerry Keister
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Chapter 7 2 Covalent Bonds and Covalent Bonds and Molecular Structure Molecular Structure Chapter 7 Chapter 7
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Chapter 7 3 Covalent Bonding Covalent Bonding In ionic bonding one atom completely loses an electron while the other gains the electron. When two similar atoms bond, none of them wants to lose or gain an electron to form an octet. When similar atoms bond, they share pairs of electrons to each obtain an octet. Each pair of shared electrons constitutes one chemical bond. Example: H + H H 2 has electrons on a line connecting the two H nuclei.
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Chapter 7 4 Covalent Bonding Covalent Bonding
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Chapter 7 5 Covalent Bonding and Orbital Overlap Covalent Bonding and Orbital Overlap As two nuclei approach each other their atomic orbitals overlap. As the amount of overlap increases, the energy of the interaction decreases. At some distance the minimum energy is reached. The minimum energy corresponds to the bonding distance (or bond length). As the two atoms get closer, their nuclei begin to repel and the energy increases. At the bonding distance, the attractive forces between nuclei and electrons just balance the repulsive forces (nucleus-nucleus, electron-electron).
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Chapter 7 6
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Chapter 7 7 Covalent Bonding Covalent Bonding Multiple Bonds Multiple Bonds It is possible for more than one pair of electrons to be shared between two atoms (multiple bonds): One shared pair of electrons = single bond (e.g. H 2 ); Two shared pairs of electrons = double bond (e.g. O 2 ); Three shared pairs of electrons = triple bond (e.g. N 2 ). Generally, bond distances decrease as we move from single through double to triple bonds. H H O O N N
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Chapter 7 8 Bond Polarity and Electronegativity Bond Polarity and Electronegativity In a covalent bond, electrons are shared. Sharing of electrons to form a covalent bond does not imply equal sharing of those electrons. There are some covalent bonds in which the electrons are located closer to one atom than the other. Unequal sharing of electrons results in polar bonds .
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Chapter 7 9 Bond Polarity and Electronegativity Bond Polarity and Electronegativity Electronegativity Electronegativity Electronegativity is the ability of an atom in a chemical bond to attract electrons to itself. Electronegativity is a scale from 0.7 (Cs) to 4.0 (F). Electronegativity is closely related to both ionization energy and electronaffinity, but applies to molecules, not ions. Electronegativity increases across a period and up a group.
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Chapter 7 10 Bond Polarity and Electronegativity Bond Polarity and Electronegativity Electronegativity Electronegativity
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Chapter 7 11 Bond Polarity and Electronegativity Bond Polarity and Electronegativity Electronegativity and Bond Polarity Electronegativity and Bond Polarity Difference in electronegativity is a gauge of bond polarity:
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McF7S - Chemistry 107: General Chemistry Chemistry for...

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