Types of Chemical Bonds
Chapter 4.1

Lewis Theory of Bonding
• Atoms and ions are stable if they have a full valence shell of electrons (noble gas configuration)
• Electrons are most stable when they are paired
• Atoms form chemical bonds to achieve a full valence shell of electrons. This may be achieved in two ways:
1.
An exchange of electrons between metal and non-metal atoms
2.
Sharing of electrons between nonmetal atoms

Lewis Diagrams
• A simplified version of a Bohr-Rutherford diagram
• The chemical symbol represents the nucleus and core electrons
• Dots around the symbol represent the valence electrons

Ionic Bonding
• An ionic bond is the electrostatic attraction between oppositely charged ions
• Ionic bonds are found in ionic compounds (ex:
NaCl, Al
2
O
3
, etc.)
• Ionic bonds involve electron transfer (one atom loses electrons and another atom gains them
• An ionic bond usually occurs between a metal and a non-metal
• Atoms held together by ionic bonds usually have a very high difference in electronegativity

Ionic Bonding

Crystal Lattice Structure
• In an ionic compound, ions will arrange themselves in a crystal lattice to maximize attractions between opposite charges and minimize repulsions between like charges

Covalent Bonding
• A covalent bond is a chemical bond in which atoms share bonding electrons
• Covalent bonds are found in molecular elements
(ex: H
H
2
2
, Cl
O, CO
2
2
, O
C
3
H
8
3
) and molecular compounds (ex:
)
• A covalent bond usually occurs between two nonmetals
• There are two types of covalent bonds:
1. Non-polar covalent
2. Polar Covalent

Covalent Bonding

The Octet Rule
• Atoms tend to gain, lose, or share electrons until they are isoelectronic with a noble gas (have the same number of electrons as a noble gas)
• The octet rule is the observation that many atoms tend to form the most stable substances when they are surrounded by eight electrons in their valence shell
NOTE:
Hydrogen is an exception. It follows the duet rule where it shares only one electron to reach an outer shell of two electrons

Lewis Structures
• A Lewis Structure is a diagram that shows the arrangement of electrons and covalent bonds in a molecule or polyatomic ion

Practice
• Draw the Lewis structure for sulfur trioxide

Practice
• Draw the Lewis structure for the chlorate ion

Exceptions to the Octet Rule
• Hydrogen always obeys the duet rule
• Carbon, Nitrogen, Oxygen, and Halogens often obey the octet rule
• In all other atoms you may see exceptions to the octet rule

Underfilled Octets
• Example: Boron trifluoride

Overfilled Octets
• Example: Sulfur hexafluoride

Practice
• Draw the Lewis structure for BrF
5

Coordinate Covalent Bonding
• A coordinate covalent bond is a covalent bond in which the electrons involved in bonding are from one atom

HOMEWORK
Required Reading: p. 192-205
(remember to supplement your notes!)
Questions: p. 200 #1-2 p. 204 #1-2 p. 205 #1-7