Covalent Bonding Vocabulary covalent bond single bond nonpolar

Covalent Bonding Vocabulary • covalent bond • single bond • nonpolar 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, Cl 2 Cl Cl 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. 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. When atoms bond covalently, they form molecules. Cl Cl This is the Lewis structure for the Cl 2 molecule.

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 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. 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 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: Dipole arrow 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: Partial charges δ+ δ- H Cl

Covalent Bonding Let’s look at another molecule, O 2. Draw the Lewis structures for the two oxygen atoms separately. O O 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, O 2. Draw the Lewis structures for the two oxygen atoms separately. O O 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, O 2. Draw the Lewis structures for the two oxygen atoms separately. O O 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, O 2. Draw the Lewis structures for the two oxygen atoms separately. O O 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. O O This is the Lewis structure for the O 2 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 O We can also draw it this way. This is called the structural formula for O 2. 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 Which of the following compounds will have covalent bonds? a) b) c) d) Na. Cl H 2 O Li 3 P CO 2 e) f) g) h) C 6 H 12 O 6 Sr. Br 2 Al 2 O 3 PCl 5

Practice Draw the Lewis structure for water. Are the bonds single, double, or triple covalent bonds. H H O Steps 1) 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. H H O Steps 1) 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. H H O Steps 1) 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. H H O There are two single covalent bonds in a water molecule.

Practice Draw the Lewis structure for PCl 3. Steps 1) Draw each atom’s Lewis structure. 2) Pair up unpaired electrons. 3) Rearrange atoms so that electron pairs are connected. Cl P Cl Cl

Practice Draw the Lewis structure for HCN. Steps 1) Draw each atom’s Lewis structure. 2) Pair up unpaired electrons. 3) Rearrange atoms so that electron pairs are connected. HC N Single bond Triple bond