Covalent Bonding

Vocabulary

• covalent bond
• single bond
• nonpolar covalent bond
• polar covalent bond
• dipole
• partial charges
• double bond
• triple bond
• molecule
• structural formula

“Dancer”, Fernando Botero Colombian, 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

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How many electrons does each

chlorine atom need to gain to have

a full octet?

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.

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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.

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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.

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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.

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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.

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Cl

Cl

This is the Lewis structure for the Cl₂ molecule.

When atoms bond covalently, they form molecules.

Covalent Bonding

Notice that each of the atoms bonded has

exactly the same electronegativity. This means

that each atom is attracting the shared

electrons exactly the same amount. Equal

sharing is called a nonpolar covalent bond.

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Cl

Cl

Covalent Bonding

In the molecule shown below, the two atoms

have different electronegativities. Hydrogen’s

electronegativity is 2.1 and chlorine’s is 3.5.

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H

Cl

Covalent Bonding

This means that even though the bonded

pair of electrons are being shared, chlorine is

pulling harder on them than is hydrogen. This

unequal sharing is called a polar covalent bond.

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H

Cl

Covalent Bonding

Polar bonds create a dipole where the shared

electrons spend more time on one side of the

bond than the other. It can be represented in

two ways:

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H

Cl

Dipole arrow

Covalent Bonding

Polar bonds create a dipole where the shared

electrons spend more time on one side of the

bond than the other. It can be represented in

two ways:

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H

Cl

Partial charges

δ+

δ-

Covalent Bonding

Let’s look at another molecule, O₂. Draw the

Lewis structures for the two oxygen atoms

separately.

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How 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.

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How 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.

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How 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.

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How 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.

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O

O

This 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.

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O

O

We 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

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Lewis Dot Structure Practice

Draw the Lewis structure for H₂O.

H

H

O

1. Draw each element’s Lewis structure separately to visualize.
2. Pair up single electrons.
3. Draw completed Lewis structure.

Lewis Dot Structure Practice

Draw the Lewis structure for H₂O.

H

H

O

1. Draw each element’s Lewis structure separately to visualize.
2. Pair up single electrons.
3. Draw completed Lewis structure.
4. Check octet rule for each element.

Lewis Dot Structure Practice

Draw the Lewis structure for PCl₃.

1. Draw each element’s Lewis structure separately to visualize.
2. Pair up single electrons.
3. Draw completed Lewis structure.

Lewis Dot Structure Practice

Draw the Lewis structure for PCl₃.

1. Draw each element’s Lewis structure separately to visualize.
2. Pair up single electrons.
3. Draw completed Lewis structure.
4. Check octet rule for each element.

Lewis Dot Structure Practice

Draw the Lewis structure for HCN.

1. Draw each element’s Lewis structure separately to visualize.
2. Pair up single electrons.
3. Draw completed Lewis structure.

Lewis Dot Structure Practice

Draw the Lewis structure for HCN.

1. Draw each element’s Lewis structure separately to visualize.
2. Pair up single electrons.
3. Draw completed Lewis structure.
4. Check octet rule for each element.

OR

C

H