Part 3: Lewis Dot Structures
and Multiple Bonds
Objectives
• To learn how to depict covalent
bonds with Lewis Dot Structures
• To understand the difference
between single, double, and triple
covalent bonds
2
Stability in Bonding
H +
atom
H 
H2 +
atom
molecule
energy
Molecule has less energy and is
more stable than atoms
Ways to represent the
hydrogen molecule:
• H2 molecular formula - indicates
number of atoms in molecule
• H-H structural formula - dash is 1
SHARED pair of electrons
• H:H dot structure (Lewis structure) use 1 dot for each electron in highest
energy level
Covalent Bonding
• Covalent bonding is the sharing of
electrons between atoms
• Because of this, the atomic orbitals
of atoms overlap one another
Orbital Overlap
Crude picture representation:
. .
ATOMIC orbitals overlapping
Refined picture representation:
.
.
MOLECULAR orbital holds 2 electrons maximum
Orbitals can not overlap completely
because of the 2 nuclei
Lewis Dot Structures of
Covalent Compounds
• Electrons of an atom are either core or
valence electrons
• Valence electrons are the outermost and
involved in chemical reactions
• They are shown in Lewis Dot structures
Valence Electrons
• Valence electrons vary by element
• Main Group element’s valence electrons
are equal to their group number
• Ex: Sodium (Na) belongs to Group 1A and
therefore has 1 valence electron.
IA
H IIA
Li Be
Na Mg
K Ca
Rb Sr
Cs Ba
VIIIA
Transition
metals
VIA VIIA He
IIIA IVA
VA
B
Al
Ga
In
Ti
N O
P S
As Se
Sb Te
Bi Po
C
Si
Ge
Sn
Pb
F Ne
Cl Ar
Br Kr
I Xe
At Rn
Let’s Do It!!!
How many valence electrons does
Potassium (K) have?
1
How many valence electrons does Antimony
(Sb) have?
5
How many valence electrons does Phosphorus
(P) have?
5
How many valence electrons does Magnesium
(Mg) have?
2
Noble Gases
VIIIA • Noble Gases in Group VIIIA have
He
Ne
Ar
Kr
Xe
Rn
either two valence electrons (He)
or eight (Ne, Ar, Kr, Xe, and Rn)
• They are extremely stable and this
is the basis for the Octet Rule elements react to attain the
electron configuration of Group
VIIIA
Neon has eight valence electrons, so its Lewis
dot symbol is:
Ne
Octet Rule
• Remember metals on the left of the
periodic table tend to lose electrons and
nonmetals on the right tend to gain
• This is to achieve a stable configuration of
8 valence electrons
Covalent Bond
• Each fluorine atom has seven valence
electrons and require one more electron to
satisfy the Octet Rule.
F F
Covalent Bond
F F
• The left fluorine has a total of eight
electrons and the right fluorine has a total of
eight valence electrons
• Nonmetallic elements react together and
share electrons in order to obtain eight
valence electrons
F F
Covalent Bond
• The two electrons in the covalent bond are
often represented by a line
• The F2 molecule can be represented using a
line (bonding pair) and dots (six lone pairs)
F F
Multiple Covalent Bonds
• Some atoms have to share more than one
electron in order to meet the Octet Rule
• Each oxygen atom has six valence
electrons and they each require two more
electrons to satisfy the Octet Rule
O
O
Multiple Covalent Bonds
O O
• Both the left and right atoms now have a
total of eight
• A double bond is represented by two single
lines and each represents two electrons
O O
Covalent Bonds
• Hydrogen is an exception
to the Octet Rule
because it only needs two
electrons to be stable
• H has one valence electron
and it requires one more
• F has seven valence
electrons and it requires
one more
H
F
H F
Covalent Bonds
H F
• The hydrogen atom now has a total of two
electrons around it and is stable
• The fluorine atom now has a total of eight
electrons around it and is stable
Objectives
• To learn how to depict covalent
bonds with Lewis Dot Structures
• To understand the difference
between single, double, and triple
covalent bonds
20