Introduction to Covalent
Compounds
Covalent molecules are formed
when atoms share electrons.
Molecular orbitals are formed when
atomic orbitals overlap.
Covalent bonds occur at a distance at
which the potential energy is at a
minimum.
• Bonded atoms
vibrate; the bond
length is the
average distance
between the atoms.
• The energy
required to break
the bond and
separate the atoms
is known as the
bond energy.
Electronegativity is the tendency of an atom
to attract bonding atoms to itself when it
bonds to another atom.
Each atom is assigned an electronegativity value. The
higher the value, the higher the tendency to attract an
electron to itself.
Bond character can be predicted by
subtracting the electronegativities of the two
atoms involved in the bond.
• The greater the difference, the higher the degree
of ionic character.
• At one extreme of the spectrum are ionic bonds,
in which the electron has been transferred from
one atom to the other.
• At the other extreme are nonpolar bonds, in
which electrons are shared equally.
– The best example of this is a diatomic molecule such
as H2.
• In between are polar covalent molecules, in
which electrons are shared, but not equally.
Nonpolar Covalent Bond
Polar Covalent Bond
Ionic Bond
Bond character can be predicted by
subtracting the electronegativities
of the two atoms involved in the
bond.
• Nonpolar covalent bond-difference of
less than 0.5
• Polar covalent bond-difference of
0.5-2.1
• Ionic bond-difference of more than
2.1
Polar molecules have a positive
end and a negative end.
• A molecule for which this
is true is a dipole.
• The strength of this
polarity is measured by
the dipole moment.
• The higher the dipole
moment, the higher the
polarity.
• As the polarity of the
molecule increases, so
does its bond strength.
Naming binary covalent
compounds
• Table 6-5 on p. 212 gives the prefixes used in
naming covalent compounds.
• The first element named is usually the first one
written in the formula-the least electronegative
element
– The root word is the name of the element.
– The prefix is used to indicate how many atoms of that
element are in the molecule.
– The prefix mono- is not used in the first word of the
name.
Naming binary covalent
compounds
• The last element in the compound is
generally the element with the higher
electronegativity.
– It is given the suffix –ide, just as in binary ionic
compounds.
– The prefix is used to indicate how many
atoms of that element are in the molecule.
– The prefix mono- is used for the second
element when only one atom of that element
is present.
Example: CO
• There is only one carbon. Since carbon is the
first element, the prefix mono- is not used.
• There is only one oxygen, but since this is the
second element, the prefix mono- is used.
• Because oxygen is the second element, we add
the suffix -ide.
• The name of this compound is:
Carbon monoxide
Example: P4O6
• There is are 4 phosphorus atoms in this
compound. The prefix for 4 is tetra-.
• There are 6 oxygen atoms in this
compound. The prefix for 6 is hexa-.
• Because oxygen is the second element,
we add the suffix -ide.
• The name of this compound is:
Tetraphosphorus hexoxide