2. Remember - Ions are atoms or groups of atoms with a charge
Chemical bonding-Introduction
A. Bond - refers to the attractive forces that hold atoms
together in compounds
B. ionic bonding - transfer of electrons from one atom to
another
Remember - Ions are atoms or groups of atoms with a charge
1. produces ionic compounds
a. solids with high melting points
b act as electrolytes when dissolved in
water or are melted
Electrolytes are substances that conduct electricity
when melted or dissolved

3. C. covalent bonding - sharing of electrons
1. produces covalent compounds
a. gas, liquids or solids with low melting points
b. generally poor electrolytes

4. Atomic number = number of Electrons
electron shells
Atomic number = number of Electrons
Electrons vary in the amount of energy they possess,
and they occur at certain energy levels or
electron shells.
Electron shells determine how an atom behaves
when it encounters other atoms

5. Octet Rule = atoms tend to gain, lose or share electrons so as to have 8 electrons
Carbon has 4 valence electrons
Needs 4 electrons
Needs 3 electrons
Nitrogen has 5 valence electrons
Needs 2 electrons
Oxygen has 6 valence electrons

6. Compounds are formed from chemically bound atoms or ions.
Bonding involves only the valence electrons.
Valence electrons are the ones in the quantum shell with largest
n value
Use the periodic chart to guide determination of valence electrons

10. A. formation of ionic compounds
II. Ionic bonding
A. formation of ionic compounds
1. attraction of oppositely charged atoms
2. anions are negative cations are positive
3. opposites attract
4. easy rule of thumb- the farther they are on the
periodic table - the more likely they will form
ionic bonds

11. B. metals (group I) and nonmetals (group VII)
1. the metals tend to loss electrons (oxidation)
2. the nonmetals to gain electrons (reduction)
Na+1Cl-1
The Na atom become isoelectronic with Neon and Cl becomes
isoelectronic with argon
Isoelectronic - same electron configuration

12. A. Formed when two atoms share two or more pairs of electrons
III. Covalent Bonding
A. Formed when two atoms share two or more pairs of electrons
B. product of a covalent bond is known as a molecule
C. Covalent bonds themselves are fairly strong
D. The attractions between the molecules is relatively weak
E. small difference in electronegativity
1. electronegativity - ability to attract a shared pair
of electrons

13. 1 electron - single, 2 electrons = double 3 electrons - triple
F. Can share
1 electron - single, 2 electrons = double 3 electrons - triple C C C C C C
H Octet rule
1. In most cases, bonding elements achieve noble gas
configuration or become isoelectronic to a noble gas
2. Finding number of Bonds
a. S = N-A

14. Atoms tend to gain, lose, or share electrons until they have eight valence electrons.
Hydrogen is an exception. It shares only one electron to reach an outer shell of two electrons

15. [ ] Formation of sodium chloride: IonicCl
· ·
Na+ [ ] Cl
· · Na +
Formation of Hydrogen chloride: (covalent) Cl
· · Cl
· · H H +
A metal and a nonmetal transfer electrons to form
an ionic compound. Two nonmetals share
electrons to form a molecular compound.

16. •• O Ba 2+ 2- Ba • O ••
BaO Mg • Cl •• •• Cl Mg 2+ - 2
MgCl2

17. Ionic compounds consist of a lattice of positive and negative ions.
NaCl:

18. Electronegativity Difference
If the difference in electronegativities is between:
1.7 to 4.0: Ionic
0.3 to 1.7: Polar Covalent
0.0 to 0.3: Non-Polar Covalent

20. Example: NaCl
Na = 0.9, Cl = 3.0
Difference is 2.1, so
this is an ionic bond!

22. Classify the following bonds as ionic, polar covalent,
or covalent: The bond in CsCl; the bond in H2S; and
the NN bond in H2NNH2.
Cs – 0.7
Cl – 3.0
3.0 – 0.7 = 2.3
Ionic
H – 2.1
S – 2.5
2.5 – 2.1 = 0.4
Polar Covalent
N – 3.0
N – 3.0
3.0 – 3.0 = 0
Covalent
9.5

23. + Lewis Structures For Covalent Bonds H H2: ® H H or H H or Cl Cl Cl +
Represents
a pair of e- H +
H2:
® H H
or H H
Bonding
electrons
or Cl Cl
· · Cl
· · +
® Cl Cl
· ·
Cl2:
Nonbonding electrons

24. Why should two atoms share electrons?
A covalent bond is a chemical bond in which two or more electrons are shared by two atoms.
Why should two atoms share electrons?
7e-
7e-
8e-
8e- F F + F
Lewis structure of F2
lone pairs F
single covalent bond
single covalent bond F
9.4

25. Hydrogen atoms are always terminal atoms
Central atoms are generally those with the lowest electronegativity.
Carbon atoms are always central atoms.
Generally structures are compact and symmetrical.

26. H H H C C O H H H

27. Lewis Structures
Draw Lewis structures for: HF
H2O:
NH3:
CH4:

29. Lewis structure of water
single covalent bonds
2e-
8e-
2e- H + O + H O H or
Double bond – two atoms share two pairs of electrons
8e-
8e-
8e-
double bonds O C or O C
double bonds
Triple bond – two atoms share three pairs of electrons
8e-
triple bond N
8e- or N
triple bond
9.4

35. : : : : SAMPLE PROBLEM 1 PROBLEM:
Write a Lewis structure for CCl2F2, one of the compounds responsible for the depletion of stratospheric ozone.
SOLUTION: Cl
Step 1: Carbon has the lowest EN and is the central atom.
The other atoms are placed around it. Cl C F F
Steps 2-4:
C has 4 valence e-, Cl and F each have 7. The sum is 4 + 4(7) = 32 valence e-. : C Cl F : :
Make bonds and fill in remaining valence electrons placing 8e- around each atom. :

36. H : H C O H : H SAMPLE PROBLEM 2
Writing Lewis Structure for Molecules with More than One Central Atom
PROBLEM:
Write the Lewis structure for methanol (molecular formula CH4O), an important industrial alcohol that is being used as a gasoline alternative in car engines.
SOLUTION:
Hydrogen can have only one bond so C and O must be next to each other with H filling in the bonds.
There are 4(1) = 14 valence e-.
C has 4 bonds and O has 2. O has 2 pair of nonbonding e-. H : H C O H : H

38. Ionic, covalent and Metallic
Third type of bonding
Ionic, covalent and Metallic
Metalic bonding
Think of a metalic bond having a sea of electrons above it and below it
This sea of electrons gives metals their metallic properties
Conductivity
e- e- e- e- e- e- e- e- e- e-
e- e- e- e- e- e- e- e-

39. malleability e- e- e- e- e- e- e- e- e- e-

40. Writing Lewis Structures for Molecules with
SAMPLE PROBLEM 3
Writing Lewis Structures for Molecules with
Multiple Bonds.
PROBLEM:
Write Lewis structures for the following: 2
(a)
Ethylene (C H
), the most important reactant in the 4
manufacture of polymers
(b)
Nitrogen (N
), the most abundant atmospheric gas 2
PLAN:
For molecules with multiple bonds, there is a
Step 5
which follows the
other steps in Lewis structure construction. If a central atom does not
have 8e -
, an octet, then e -
can be moved in to form a multiple bond.
SOLUTION:
(a)
There are 2(4) + 4(1) = 12 valence e -
. H can have only
one bond per atom. C H C H : :
(b) N
has 2(5) = 10 valence e -
. Therefore a triple bond is required to make 2
the octet around each N. N : . N : N : .

41. Space filling Model
ball and stick model
SF4