Organic Chem 1
Organic Chemistry, Fourth Edition
Janice Gorzynski Smith
University of Hawai’i
Chapter 1
Lecture Outline
Prepared by Layne A. Morsch
The University of Illinois - Springfield
Copyright © 2014 The McGraw-Hill Companies, Inc. Permission required for reproduction or display.
1
Bonding
• Bonding is the joining of two atoms in a stable arrangement. • Through bonding, atoms attain a complete outer shell of valence electrons (stable noble gas configuration).
• Atoms can form either ionic or covalent bonds to attain a complete outer shell (octet rule for second row elements). • Ionic bonds result from the transfer of electrons from one element to another.
• Covalent bonds result from the sharing of electrons between two nuclei.
2
Valence Electrons
• Second row elements can have no more than eight electrons around them. For neutral molecules, this has two consequences:
• Atoms with one, two, three, or four valence electrons form one, two, three, or four bonds, respectively, in neutral molecules (e.g., BF3, CH4).
• Atoms with five or more valence electrons form enough bonds to give an octet (e.g., NH3). This results in the following equation:
3
Lewis Structures
Lewis structures are electron dot representations for molecules. General rules for drawing Lewis structures:
1. Draw only the valence electrons.
2. Give every second-row element no more than eight electrons. 3. Give each hydrogen two electrons.
A solid line indicates a twoelectron covalent bond.
4
How to Draw a Lewis Structure
Step [1] Arrange atoms next to each other that you think are bonded together.
• Always place hydrogen and halogens on the periphery because they form only one bond each.
• Place no more atoms around an atom than the number of bonds it usually forms.
5
How to Draw a Lewis Structure
Step [2]
•
•
•
•
Count the electrons.
Count the number of valence electrons from all atoms.
Add one electron for each negative charge.
Subtract one electron for each positive charge.
Janice Gorzynski Smith
University of Hawai’i
Chapter 1
Lecture Outline
Prepared by Layne A. Morsch
The University of Illinois - Springfield
Copyright © 2014 The McGraw-Hill Companies, Inc. Permission required for reproduction or display.
1
Bonding
• Bonding is the joining of two atoms in a stable arrangement. • Through bonding, atoms attain a complete outer shell of valence electrons (stable noble gas configuration).
• Atoms can form either ionic or covalent bonds to attain a complete outer shell (octet rule for second row elements). • Ionic bonds result from the transfer of electrons from one element to another.
• Covalent bonds result from the sharing of electrons between two nuclei.
2
Valence Electrons
• Second row elements can have no more than eight electrons around them. For neutral molecules, this has two consequences:
• Atoms with one, two, three, or four valence electrons form one, two, three, or four bonds, respectively, in neutral molecules (e.g., BF3, CH4).
• Atoms with five or more valence electrons form enough bonds to give an octet (e.g., NH3). This results in the following equation:
3
Lewis Structures
Lewis structures are electron dot representations for molecules. General rules for drawing Lewis structures:
1. Draw only the valence electrons.
2. Give every second-row element no more than eight electrons. 3. Give each hydrogen two electrons.
A solid line indicates a twoelectron covalent bond.
4
How to Draw a Lewis Structure
Step [1] Arrange atoms next to each other that you think are bonded together.
• Always place hydrogen and halogens on the periphery because they form only one bond each.
• Place no more atoms around an atom than the number of bonds it usually forms.
5
How to Draw a Lewis Structure
Step [2]
•
•
•
•
Count the electrons.
Count the number of valence electrons from all atoms.
Add one electron for each negative charge.
Subtract one electron for each positive charge.