2. Why do Atoms Bond?
• Stable Arrangement
– full outer energy level
3. What is a Covalent Bond?
• Covalent Bond
– A chemical bond that
results from sharing
valence electrons
• Molecule
– When 2 or more atoms
bond covalently
– The shared electrons are
part of the outer energy
level
– Generally form between
non-metallic elements
4. Bond Formation
• Diatomic Molecules form when TWO
atoms form a molecule
– Example: N2 , F2
– The sharing of one pair of electrons gives
each atom a stable noble gas configuration
6. Single Covalent Bonds
• Only one pair of electrons are shared
• The shared electrons belong to each atom
simultaneously
7. Lewis Structure
• Represent the arrangement of electrons in
a molecule
• A line or pair of vertical dots between the
symbols represent a single covalent bond
8. Lewis Structures
• Group 16 can share 2 electrons and form
2 covalent bonds
• Group 15 can form 3 covalent bonds with
atoms of nonmetals
• Group 14 can form four covalent bonds
10. Covalent Bonds Continued
• Sigma Bond
– Single covalent bond
– The shared electrons is in an area centered between the
two atoms
• Double Bonds
– Two pairs of electrons are shared between the two atoms
– Example: Oxygen
• Triple Bonds
– 3 paris of electrons are shared between 2 atoms
– Example: Nitrogen
• Pi Bonds
– If bonds have multiple bonds, they have both a sigma and
a pi bond. Example: A triple covalent bond has 1 sigma
and 2 pi bonds
11. Strength of Covalent Bonds
• Bond Length
– The distance between the two
bonded nuclei at the position
of maximum attraction
– As the number of shared
electron pairs increases the
bond length decreases
– The shorter the bond length
the stronger the bond
• So, the weakest bond is a single
covalent bond and the strongest
is a triple covalent bond
12. Bonds and Energy
• Energy is released when a bond forms
• Energy must be added to break a bond
• The amount of energy required to break a
covalent bond is called the bond dissociation
energy. It is always positive
• Endothermic Reaction- a greater amount of
energy is required to break the existing bond
in the reactants than is released
• Exothermic Reaction- more energy is released
during broduct bond formation than is required
to break bonds in the reactants.
14. Basic Rules
• Must be a binary molecular compound of 2
NON METALS
1. The first element in the formula is named
first using the ENTIRE elements name
2. The second element in the formula is
named using its root and adding the suffix
–ide.
3. Prefixes are used to indicate the number
of atoms of each element that are present
in the compound.
16. Exceptions to the rules
• Never use mono when naming the first
element
• If using a prefix results in two consecutive
vowels, drop one to make it easier to say
Example: CO
Carbon Monoxide not
Monocarbon Monooxide
18. Common Names
• Do you drink Dihydrogen Monoxide?
• Do you use Dinitrogen Monoxcide at the
dentist?
• Some binary molecular compounds have
common names
• They are water, ammonia, hydrazine, and
nitric oxide, and nitrous oxide
19. Let’s Name Acids
• If a compound produces H ions in a
compound it is an acid.
• 2 types
– Binary
• H and one other element
– Oxyacids
• A polyatomic ion containing one or more oxygen
atoms
20. Binary Acids
1. The first word has the prefix hydro to
name the H part of the compound
2. The rest of the 1st word consists of a form
of the root of the 2nd element plus the
suffix –ic
3. The second word is always acid
22. Exception to rule
• Acids containing more than 2 elements
with NO OXYGEN
• Use the name of the polyatomic ion as the
root
23. Naming Oxyacids
1. Root of the oxyacid and the prefix per- or
hypo-
1. H are not used as part of the name
2. If the name ends with -ate replace it with
–ic
3. If the name ends with –ite replace it with
–ous
4. The second word is always acid
26. Writing Formulas from Names
• The prefixes indicated the number of each
atom present
• Remember all binary acids contain H and
one other element
• You will need to know the name of the
common oxyanions
28. Structures
• Molecular-element symbols and
subscripts
– Example: PH3
• Ball and stick model- atoms are
represented by colored spheres
• Structural formula-
– Most useful
– Uses letter symbols and bonds
30. Resonance Structures
• It is possible to have more than one lewis
structure
• When more than one valid lewis structure
can be written for a molecule or ion
• Behaves as if it has only one structure
• Actual bond length is the average of the
bonds in the resonance structures
31. Exceptions to the Octet
• Odd number of valence electrons
• Coordinate covalent bond-when one atom
donates both of the electrons to be shared
with an atom or ion that needs two
electrons to form a stable electron
arrangement.
• Figure 8.16 in your book!
• Expanded octets-a central atom with more
than 8 valence electrons
33. VSEPR Model
• The model used to determine the
molecular shape
• Valence Shell Electron Pair Repulsion
• Based on an arrangement that minimizes
the repulsion of shared and unshared
electron pairs
34. Bond Angle
• The electron pairs in a molecule repel
each other like balloons tied together
• This causes the atoms to be positioned at
a fixed angle to one another
• The angle formed by two terminal atoms
and the central atom is a bond angle
35. Hybridization
• Occurs when 2 things are combined and
the result has characteristics of both
• Hybridization is a process in which atomic
orbitals mix and form new identical hybrid
orbitals.
36. Hybridization
• Hybrid- When two things are combined
and the result has characteristics of both
• Hybridization- a process in which atomic
orbitals mix and form new, identical
orbitals
