4.1 Types of Chemical Bonds

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: An exchange of electrons between metal and non-metal atoms 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 (H2O, CO2, C3H8) A covalent bond usually occurs between two non-metals There are two types of covalent bonds: Non-polar covalent 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 Structure A Lewis Structure is a diagram that shows the arrangement of electrons and covalent bonds in a molecule or polyatomic ion

Steps for Drawing Lewis Structures Pg. 197

Practice Draw the Lewis structure for Sulfur trioxide 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 Overfilled Octets Ex: Boron trifluoride Ex: 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 Questions: P.200 #1-2 P.204 #1-2 (remember to supplement your notes!) Questions: P.200 #1-2 P.204 #1-2 p.205 #1-7