5 Steps to a 5 AP Chemistry

Bonding  165

 Ionic bonds can also result from the interaction of polyatomic ions.

 The attraction of the opposite charges (anions and cations) forms the ionic bond.

 The crisscross rule can help determine the formula of an ionic compound.

 In covalent bonding two atoms share one or more electron pairs.

 If the electrons are shared equally, the bond is a nonpolar covalent bond, but unequal

sharing results in a polar covalent bond.

 The element that will have the greatest attraction for a bonding pair of electrons is

related to its electronegativity.

 Electronegativity values increase from left to right on the periodic table and decrease

from top to bottom.

 The N – A =S rule can be used to help draw the Lewis structure of a molecule.

 Molecular geometry, the arrangement of atoms in three-dimensional space, can be pre-

dicted using the VSEPR theory. This theory says the electron pairs around a central atom

will try to get as far as possible from each other to minimize the repulsive forces.

 In using the VSEPR theory, first determine the electron-group geometry, then the

molecular geometry.

 The valence bond theory describes covalent bonding as the overlap of atomic orbitals to

form a new kind of orbital, a hybrid orbital.

 The number of hybrid orbitals is the same as the number of atomic orbitals that were

mixed together.

 There are a number of different types of hybrid orbital, such as sp, sp^2 , and sp^3.

 In the valence bond theory, sigma bonds overlap on a line drawn between the two nuclei,

while pi bonds result from the overlap of atomic orbitals above and below a line connect-

ing the two atomic nuclei.

 A double or triple bond is always composed of one sigma bond and the rest pi.

 In the molecular orbital (MO) theory of covalent bonding, atomic orbitals form molec-

ular orbitals that encompass the entire molecule.

 The MO theory uses bonding and antibonding molecular orbitals.

 The bond order is (# electrons in bonding MOs – # electrons in anti-bonding MOs)/2.

 Resonance occurs when more than one Lewis structure can be written for a molecule.

The actual structure of the molecule is an average of the Lewis resonance structures.

 The higher the bond order, the shorter and stronger the bond.

 Paramagnetism, the attraction of a molecule to a magnetic field, is due to the presence

of unpaired electrons. Diamagnetism, the repulsion of a molecule from a magnetic field,

is due to the presence of paired electrons.