Chemical Bonding: The Covalent Bond Model

Chemical Bonds Forces that hold atoms to each other within a molecule or compound

Ionic Bonds Attractive force holding oppositely charged ions together Ions can be monoatomic or polyatomic Involve “+” charged metal ion (or NH 4 + ) and “–” charged non-metal ion Results in formation of an ionic compound

Covalent Bonds Attractive force between a non-metal and a non-metal Involves sharing of electrons Results in formation of a covalent compound (a true molecule)

Covalent bonding can occur due to orbital overlap

Lewis structures can help determine how many covalent bonds will form

What are these? Bonding electrons Non-bonding electrons Single bond Double bond Triple bond Coordinate covalent bond

Drawing Lewis Structures of Molecules Count the total number of valence electrons available (add or subtract for polyatomic ions) Place chemical symbols in tentative arrangement Make single bonds Fill “outer” atoms with non-bonding pairs Place remaining electrons on central atom(s) Check the structure and make double or triple bonds if needed

Electronegativity How strongly an atom pulls electrons towards itself

Using electronegativity to predict bond type Non-polar covalent (electroneg dif <0.5) Polar covalent (electroneg dif ) Ionic (electroneg dif >1.5)

VSEPR Method for predicting molecular geometry

Bond polarity and molecule geometry are used together to predict molecule polarity