2. 2
Objectives
–Explain the role and location of
electrons in a covalent bond.
–Describe the change in energy and
stability that takes place as a
covalent bond forms.
–Compare covalent and ionic
compounds.
3. 3
Bonds are…
Forces that hold groups of
atoms together and make them
function as a unit. Two types:
1) Ionic bonds – transfer of
electrons (gained or lost; makes formula unit)
2) Covalent bonds – sharing of
electrons. The resulting
particle is called a “molecule”
4. 4
Molecules
The simplest example of sharing
electrons is found in diatomic
molecules.
For example, air contains oxygen
molecules, consisting of two oxygen
atoms joined covalently (O2)
Air also contains hydrogen molecules,
consisting of two hydrogen atoms join
covalently (H2)
5. 5
How does H2 form?
Both nucleus repel each other,
since they both have a positive
charge (like charges repel).
++
(diatomic hydrogen molecule)
+ +
6. 6
How does H2 form?
++
But, the nuclei are attracted to
the electrons
They share the electrons, and
this is called a “covalent bond”,
and involves only NONMETALS!
7. 7
Covalent bonds
Nonmetals hold on to their valence
electrons.
They can’t give away electrons to bond.
–But still want noble gas configuration.
Nonmetals get it by sharing valence
electrons with each other = covalent
bonding
By sharing, both atoms get to count
the electrons toward a noble gas
configuration.
8. 8
Energy and Stability
Most individual atoms have low stability.
– Remember, if an atom doesn’t have eight
valence electrons they are unstable.
They become more stable when they are part of
a compound.
Individual atoms also have higher potential
(stored) energy.
When atoms are bonded they are at their lowest
potential energy.
The distance between two bonded atoms at their
lowest potential energy is the bond length
17. 17
Covalent bonding
Fluorine has seven valence electrons
A second atom also has seven
By sharing electrons…
…both end with full orbitals
F F
18. 18
Covalent bonding
Fluorine has seven valence electrons
A second atom also has seven
By sharing electrons…
…both end with full orbitals
F F
8 Valence
electrons
19. 19
Covalent bonding
Fluorine has seven valence electrons
A second atom also has seven
By sharing electrons…
…both end with full orbitals
F F
8 Valence
electrons
20. 20
A Single Covalent Bond is...
A sharing of two valence electrons.
Only nonmetals and hydrogen form
covalent bonds.
Different from an ionic bond
because they actually form
molecules.
H - H
21. 21
Multiple Bonds
Sometimes atoms share more than
one pair of valence electrons.
A double bond is when atoms share
two pairs of electrons O = O
A triple bond is when atoms share
three pairs of electrons (6 total) N N
What’s the deal
with the oxygen
dot diagram?
22. 22
Bond Strength
The shorter the bond the stronger the
bond
–Triple bond > double bond > single
bond
23. 23
Types of Covalent Bonds
A covalent bond in which the bonding
electrons in the molecular orbital are
shared equally is a nonpolar covalent
bond.
A covalent bond in which the bonding
electrons in the molecular orbital are
shared unequally is a polar covalent
bond.
25. 25
Ionic Compounds vs. Covalent Compounds
Ionic
compounds
The Union of a metal
and nonmetal
Transferred
Electrostatic
Strong
Solid
High
Good
Subject
Definition
How are the electrons
arranged
Forces that hold the
bond together
Strength of Bonds
(weak or strong)
State of matter @ room
temperture
Melting Point & Boiling
Point
Conduction
Covalent
compounds
The union of two or more
nonmetals/metalloid
Shared
Electrostatic
Weak
Gas or Liquid
Low
Poor
