Lewis Dot Structures-Ions
• OH-
Resonance Structures
• When one or more Lewis structure can be
drawn
• Example
SO3
Radicals
• When there is an odd number of electrons
• They are very reactive
• Example
NO2
Expanded Octet
• Elements that can have more than 8 electrons
in their outermost shell (examples: sulfur,
phosphorous, silicon and chlorine)
• Example
PCl5
Bonds
Bonds
Ionic
Covalent
Polar
Non
Polar
Bonds
• Atoms stick
together to form
molecules
• Some atoms want
to give electrons,
some others want
to get electrons.
Why? To have 8
electrons in their
outermost shell
Sometimes…
• Atoms are transferred (stolen)
• Atoms are shared evenly
• Atoms are shared unevenly
Atoms get together to form two types
of bonds:
• Ionic
• Covalent
Ionic
• metal + nonmetal
• Nonmetals are highly
electronegative (want an
electron) and metals are
not very electronegative
(want to get rid of an
electron)
• This bond is not going to
be shared. The nonmetal
will be “stealing” the
metal’s electron
Example ionic bond: NaCl
Covalent bonds
• Nonmetal + nonmetal or
Nonmetal + metalloid
• Because both elements are nonmetals, they
tend to have the same electronegativity. So
they share electrons
Classify the following as ionic or
covalent bonds
•
•
•
•
•
BrO3
CO
NaCl
Cu2O
Li2O
Two types of covalent bonds
• Non polar
O-O. Same atom so it has the same electronegativity.
They will be sharing electrons evenly
• Polar
H-F. Fluorine is more electronegative so electrons will
be attracted to it. This bond has an uneven sharing of
electrons (H will have a slightly positive charge and F
will have a slightly negative charge)
Exercises- classify the following as
polar covalent or non polar covalent
bonds
•
•
•
•
H-O-H
F-F
NF3
CS2
•
•
•
•
PC
NPC
PC
NPC
Another way to determine if a bond is
ionic, polar covalent or nonpolar
covalent: Look at the electronegative
numbers of each element
• If the difference between the numbers is:
– Less than 0.5= non polar covalent bond
– Between 0.5 and 1.9= polar covalent bond
– Greater than 1.9= ionic bond
Summary
• How do you know whether a bond is ionic or
covalent?
1- recognize whether the elements are metals or
nonmetals
2- Use the electronegativity chart
Come up with five ionic bonds, five
polar covalent bonds and five
nonpolar covalent bonds