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Covalent Bonding
Vocabulary• covalent
bond• single bond• double bond• triple bond• molecule• structural
formula“Dancer”, Fernando Botero
Columbian, 1982
Review
What is an ionic bond?
What if?
If an ionic bond requires one atom to lose electrons and one atom to gain electrons, how could two atoms bond if both atoms do not want to lose electrons but still must follow the octet rule?
What if?
Let’s look at an example: chlorine gas, Cl2
How many electrons does each chlorine atom need to gain to havea full octet?
Cl Cl
What if?
Because neither chlorine atom is willing to to give up an electron, they can not form an ionic bond. Instead each atom can SHARE one electron with the other atom to fulfill the octet rule for each.
Cl Cl
What if?
Because neither chlorine atom is willing to to give up an electron, they can not form an ionic bond. Instead each atom can SHARE one electron with the other atom to fulfill the octet rule for each.
Cl Cl
What if?
Because neither chlorine atom is willing to to give up an electron, they can not form an ionic bond. Instead each atom can SHARE one electron with the other atom to fulfill the octet rule for each.
Cl Cl
What if?
Notice that by sharing, each atom now has 8 valence electrons around it and follows the octet rule: the 7 it originally had and 1 from the other atom.
Cl Cl
Covalent Bonding
This sharing of electrons is called a covalent bond. Because only one electron is being shared from each atom in this example, it is called a single covalent bond.
Cl Cl This is the Lewis structure for the Cl2 molecule.
When atoms bond covalently, they form molecules.
Covalent Bonding
Let’s look at another molecule, O2. Draw the
Lewis structures for the two oxygen atoms separately.
O OHow do you think these two atoms can bond?How many electrons does each atom need to gain or share to achieve an octet?
Covalent Bonding
Let’s look at another molecule, O2. Draw the
Lewis structures for the two oxygen atoms separately.
O OHow do you think these two atoms can bond?How many electrons does each atom need to achieve an octet?
Covalent Bonding
Let’s look at another molecule, O2. Draw the
Lewis structures for the two oxygen atoms separately.
O OHow do you think these two atoms can bond?How many electrons does each atom need to achieve an octet?
Covalent Bonding
Let’s look at another molecule, O2. Draw the
Lewis structures for the two oxygen atoms separately.
O OHow do you think these two atoms can bond?How many electrons does each atom need to achieve an octet?
Covalent Bonding
Look at each atom now. Each atom is sharing two electrons with the other atom and now each has 8 valence electrons.
O OThis is the Lewis structure for
the O2 molecule.Because each atom is sharing 2 valence electrons, this is called
a double covalent bond.
Covalent Bonding
Look at each atom now. Each atom is sharing two electrons with the other atom and now each has 8 valence electrons.
O OWe can also draw it this way. This is called the structural
formula for O2. Each line represents two electrons.
Covalent Bonding
Important covalent bonding notes:• sharing of electrons to achieve an octet
(hydrogen is a notable exception because it only needs two valance electrons)• occur between non-metal atoms• can be single, double, or triple bond
Practice
a) NaClb) H2O
c) Li3P
d) CO2
e) C6H12O6
f) SrBr2
g) Al2O3
h) PCl5
Which of the following compounds will have covalent bonds?
Practice
Draw the Lewis structure for water. Are the bonds single, double, or triple covalent bonds.
HH
OSteps1) Draw each atom’s
Lewis structure.2) Pair up unpaired
electrons.
Practice
Draw the Lewis structure for water. Are the bonds single, double, or triple covalent bonds.
HH
OSteps1) Draw each atom’s
Lewis structure.2) Pair up unpaired
electrons.3) Rearrange atoms
so that electron pairs are connected.
Practice
Draw the Lewis structure for water. Are the bonds single, double, or triple covalent bonds.
Steps1) Draw each atom’s
Lewis structure.2) Pair up unpaired
electrons.3) Rearrange atoms
so that electron pairs are connected.
HH
O
Practice
Draw the Lewis structure for water. Are the bonds single, double, or triple covalent bonds.
There are two single covalent bonds in a water molecule.
HH
O
Practice
Draw the Lewis structure for PCl3.
Steps1) Draw each atom’s
Lewis structure.2) Pair up unpaired
electrons.3) Rearrange atoms so
that electron pairs are connected.
PCl ClCl
Practice
Draw the Lewis structure for HCN.
Steps1) Draw each atom’s
Lewis structure.2) Pair up unpaired
electrons.3) Rearrange atoms so
that electron pairs are connected.
CH NSingle bond
Triple bond