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 atoms2. Sharing of electrons between non-

metal 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, Al2O3, 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: H2, Cl2, O3) and molecular compounds (ex: H2O, CO2 C3H8)

• A covalent bond usually occurs between two non-metals

• There are two types of covalent bonds:1. Non-polar covalent2. 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 BrF5

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