The document discusses different types of chemical bonds including ionic bonds and covalent bonds. Ionic bonds involve the transfer of electrons between metals and non-metals, resulting in ionic compounds with high melting and boiling points that conduct electricity when melted or in solution. Covalent bonds involve the sharing of electrons between non-metal atoms, resulting in molecules with low melting and boiling points that do not conduct electricity. The document also discusses metallic bonding and how metal atoms are held together by valence electrons that are delocalized throughout the structure.

1. Prentice-Hall ©2002 Burns 4/e Chapter 8 Slide 1 of 69
Chemical Bonds
• Chemical Bonds
• The attractive forces that hold atoms
together in molecules.
• Ionic Bonds
• Involve the transfer of electrons
(it conducts electricity)
• Covalent Bonds
• Involve the sharing of electrons

2. Prentice-Hall ©2002 Burns 4/e Chapter 8 Slide 2 of 69
IONIC BONDS
• Exchange of electrons
• Metal with non-metal
• high melting point
• High boiling point
• brittle
• melt, solution conducts electricity

3. Prentice-Hall ©2002 Burns 4/e Chapter 8 Slide 3 of 69
Ionic Compounds in Solution
H2O
When ionic compounds are dissolved
in water, they dissociate to form
aqueous ions:
NaCl(s) Na+(aq) + Cl-(aq)
The resulting solution conducts
electricity and is called an
electrolyte.

4. Prentice-Hall ©2002 Burns 4/e Chapter 8 Slide 4 of 69
The
Structure of
Salt
Sodium
Chloride
(NaCl)

5. Prentice-Hall ©2002 Burns 4/e Chapter 8 Slide 5 of 69
Metals physical properties
Tell me please?
?
?
?

6. Prentice-Hall ©2002 Burns 4/e Chapter 8 Slide 6 of 69
Metallic Bonding
Metallic Bonding is the type of
bonding found in metallic crystals.
A metallic solid can be pictured as a
three-dimensional array of positive
ions that remain fixed in a crystal
lattice while the loosely-held valence
electrons move freely throughout the
crystal.

7. Prentice-Hall ©2002 Burns 4/e Chapter 8 Slide 7 of 69
A Model of Metallic Bonding
The fluid-like
movements of
the valence
electrons make
metals good
conductors of
heat and
electricity.

8. Prentice-Hall ©2002 Burns 4/e Chapter 8 Slide 8 of 69
Compare and contrast ionic and
covalent bonds.
Ionic Bonds
• Exchange of
electrons
• metal/non-metal
• high mp/bp
• brittle
• melt, solution
conduct electricity.
Covalent
• Sharing electrons
• non-metal/non-metal
• Molecular (low mp/bp)
• Macromolecular (high
mp/bp)
• Non conductors

9. Prentice-Hall ©2002 Burns 4/e Chapter 8 Slide 9 of 69
Covalent Bonds
Classify a covalent bond… as polar
or non polar.
Polar Bonds result from the unequal
sharing of electrons.
Unequal sharing results when there is
a difference electronegativity between
the atoms involved.

10. Prentice-Hall ©2002 Burns 4/e Chapter 8 Slide 10 of 69
Polar and non-polar bonds
H-H is non-polar because H & H have
the same electronegativity.
Cl-Cl is non-polar because Cl & Cl
have the same electronegativity.
H-Cl is polar because H & Cl have
different Electronegativities.
( H = 2.1, Cl = 3.0 )

11. Prentice-Hall ©2002 Burns 4/e Chapter 8 Slide 11 of 69
Ionic Character Increases as the
Difference in Electronegativity Increases
Electronegativity difference
0.4 1.7

12. Prentice-Hall ©2002 Burns 4/e Chapter 8 Slide 12 of 69
Diatomic Elements
p.72

13. Prentice-Hall ©2002 Burns 4/e Chapter 8 Slide 13 of 69
Ionic Character Increases as the
Difference in Electronegativity Increases
Electronegativity difference
0.4 1.7

14. Prentice-Hall ©2002 Burns 4/e Chapter 8 Slide 14 of 69
Compare and contrast ionic and
covalent bonds.
Ionic Bonds
• Exchange of
electrons
• metal/non-metal
• high mp/bp
• brittle
• melt, solution
conduct electricity
Covalent
• Sharing electrons
• non-metal/non-metal
• Molecular (low
mp/bp)
• Macromolecular
(high mp/bp)
• Non conductors

15. Prentice-Hall ©2002 Burns 4/e Chapter 8 Slide 15 of 69
Electronegativity
Generally speaking, atoms to the
right and top of the periodic table
have greater electronegativities.
F is the most electronegative of the
elements with an electronegativity
of 4.
Cs is the least electronegative at 0.7.

16. Prentice-Hall ©2002 Burns 4/e Chapter 8 Slide 16 of 69
Non-polar, Polar, Ionic
There is a continuum between non-
polar covalent bonds to ionic bonds.
Non-polar bond have no difference in
electronegativity between the atoms.
Ionic bonds have the greatest
difference in electronegativity
between the atoms.
(ΔEN>1.7)
Polar covalent bonds have an
intermediate difference in
electronegativity between the atoms.

17. Prentice-Hall ©2002 Burns 4/e Chapter 8 Slide 17 of 69
Chemical Bonds
• Chemical Bonds
• The attractive forces that hold atoms
together in molecules.
• Ionic Bonds
• Involve the transfer of electrons
• Covalent Bonds
• Involve the sharing of electrons

18. Prentice-Hall ©2002 Burns 4/e Chapter 8 Slide 18 of 69
Ionic Character Increases as the
Difference in Electronegativity Increases
Electronegativity difference
0.4 1.7

19. Prentice-Hall ©2002 Burns 4/e Chapter 8 Slide 19 of 69
Compare and contrast ionic and
covalent bonds.
Ionic Bonds
• Exchange of
electrons
• metal/non-metal
• high mp/bp
• brittle
• melt, solution
conduct electricity
Covalent
• Sharing electrons
• non-metal/non-metal
• Molecular (low
mp/bp)
• Macromolecular
(high mp/bp)
• Non conductors

20. Prentice-Hall ©2002 Burns 4/e Chapter 8 Slide 20 of 69
Metallic Bonding
Metallic Bonding is the type of
bonding found in metallic crystals.
A metallic solid can be pictured as a
three-dimensional array of positive
ions that remain fixed in a crystal
lattice while the loosely-held valence
electrons move freely throughout the
crystal.

21. Prentice-Hall ©2002 Burns 4/e Chapter 8 Slide 21 of 69
A Model of Metallic Bonding
The fluid-like
movements of
the valence
electrons make
metals good
conductors of
heat and
electricity.

22. Prentice-Hall ©2002 Burns 4/e Chapter 8 Slide 22 of 69
K =
0.8
Na =
0.9
Ca =
1.0
Be =
1.5
Si =
1.8
H =
2.1
S =
2.5
C =
2.5
Br =
2.8
Cl =
3.0
N =
3.0
O =
3.5
ELECTRONEGATIVITY
I= 2.5, Mg= 1.2, F= 4

23. Prentice-Hall ©2002 Burns 4/e Chapter 8 Slide 23 of 69
Chemical Bonds
• Chemical Bonds
• The attractive forces that hold atoms
together in molecules.
• Ionic Bonds
• Involve the transfer of electrons
• Covalent Bonds
• Involve the sharing of electrons

24. Prentice-Hall ©2002 Burns 4/e Chapter 8 Slide 24 of 69
Lewis Structures
Drawing of the electrons of the outer
energy level.
“Valence Electrons”
(Dots around the element)
6C:1s2 2s2 2p2
Valence electrons=4

25. Prentice-Hall ©2002 Burns 4/e Chapter 8 Slide 25 of 69
Octet Rule:
When ionic bonds are formed, metals
lose valence electrons so that the
electron configuration becomes like a
noble gas, leaving it with eight outer
electrons.
Non-metals gain electrons to become
like the next higher noble gas, usually
having 8 valence electrons.

26. Prentice-Hall ©2002 Burns 4/e Chapter 8 Slide 26 of 69
• Main group metals lose all their
valence electrons to form cations:
• This loss of electrons is called
oxidation.
Na. Na+ + e-
Mg: Mg2+ + 2 e-
:Al. Al 3+ + 3 e-
Ions

27. Prentice-Hall ©2002 Burns 4/e Chapter 8 Slide 27 of 69
Non-metals gain electrons to have
the noble gas configuration and form
anions:
This process is called reduction.
:Cl. + e- :Cl:- chloride
:O: + 2e- :O:2- oxide
:N. + 3e- :N:3- nitride
Anion Formation
....::
::

28. Prentice-Hall ©2002 Burns 4/e Chapter 8 Slide 28 of 69
Preserve Electroneutrality
When ions combine, electroneutrality
must be preserved.
In the formation of magnesium chloride,
2 Cl- ions must balance a Mg2+ ion:
Mg2+ + 2 Cl- MgCl2
In the formation of magnesium nitride,
3 Mg2+ ions balance 2 N3- ions:
3 Mg2+ + 2N3- Mg3N2

29. Prentice-Hall ©2002 Burns 4/e Chapter 8 Slide 29 of 69
Octet Rule
• Recognize the
importance of the octet
rule.
• Atoms tend to gain lose
or share electrons so that
there are eight electrons
in the outer shell.
(except those that
become like He)

30. Prentice-Hall ©2002 Burns 4/e Chapter 8 Slide 30 of 69
Electronegativity
Electronegativity is defined as the
ability of an atom to attract electron
density to itself when joined to
another atom in a chemical bond.
The most electronegative elements
have the greatest attraction for
electrons.

31. Prentice-Hall ©2002 Burns 4/e Chapter 8 Slide 31 of 69
Insert Figure
8.6
Increase
Electronegativities of Elements
Increase