Chapter 13
Chemical bond: Holds atoms together
Bond energy: Energy required to break bond
Ionic bond: Electrons are transferred from one atom to another. Occurs between a
metal and nonmetal
The nonmetal completes its valence orbital shell, while the metal loses
electrons. Both achieve noble gas configurations
A cation is smaller than its parent atom because an electron is removed
An anion is significantly larger than its parent atom
Coloumb’s Law: Energy of interaction between a pair of ions:
V = 2.31 E-19 J nm (Q1Q2/r)
Negative sign indicates an attractive force, which means the ion pair has a
lower energy than separated ions
Ion size depends on # of electrons and # of protons
Isoelectronic ions have the same number of electrons, so just look at the
number of protons (ion size varies inversely with proton #)
Covalent bonds: Electrons are shared
Polar Covalent means that the electrons are not shared equally, which is due
to the electronegativity
oElectronegativity: ability to attract shared electrons to itself
Bond polarity can be measured using dipole moments
Dipole moment = ø = QR
Molecules can have polar bonds, but no dipole moments:
A-B-A (Linear), A-B<AA, or tetrahedral
Electrostatic potential diagram: Red indicates region with most electrons, blue is the
opposite
Lewis Structures:
Determine the total # of valence electrons, identify central and terminal atoms,
write skeletal structure with one bond, then add double bonds as necessary to
complete octet & valence orbitals
Resonance structures: When more than one valid Lewis structure can be written.
The true structure is an average between them
To find out which is most correct, use Formal charge
F.C. = # of electrons in free atom - # of lone pair electrons – ½ # of bond pair
electrons
