Identifying Bonds(Ionic vs. Covalent)

Double & Triple

Covalent Bonds

How can you tell if a bond is IONIC or COVALENT?

Nonmetals & Metals = ionic bond

All Nonmetals = covalent bond

Writing Covalent Formulas

Place the nonmetal furthest to the left on the periodic table first. If both elements are in the same group/family then place the element closest to the top first.

Examples: Cl + H = HCl

O + 2H = H2O

4Cl + C = CCl4

Steps for Building a Dot StructureSteps for Building a Dot StructureSteps for Building a Dot StructureSteps for Building a Dot Structure

Ammonia, NHAmmonia, NH33

1. Decide on the central atom; never H. 1. Decide on the central atom; never H. Therefore, N is central on this oneTherefore, N is central on this one

2. Add up the number of valence 2. Add up the number of valence electrons that can be used.electrons that can be used.

H = 1 and N = 5H = 1 and N = 5

Total = (3 x 1) + 5 Total = (3 x 1) + 5

= 8 electrons / 4 pairs= 8 electrons / 4 pairs

3. 3. Form a single bond between the Form a single bond between the central atom and each surrounding central atom and each surrounding atom (each bond takes 2 electrons!)atom (each bond takes 2 electrons!)

H H

H

N

Building a Dot StructureBuilding a Dot Structure

H•• H

H

N4. 4. Remaining electrons form Remaining electrons form LONE PAIRS to complete the LONE PAIRS to complete the octet as needed (or duet in the octet as needed (or duet in the case of H).case of H).

3 BOND PAIRS and 1 LONE PAIR.3 BOND PAIRS and 1 LONE PAIR.

5.5. Check to make sure there are 8 Check to make sure there are 8 electrons around each atom electrons around each atom except H. H should only have 2 except H. H should only have 2 electrons. This includes SHARED electrons. This includes SHARED pairs. pairs.

Building a Dot StructureBuilding a Dot Structure

6. 6. If you have more electrons in the drawing If you have more electrons in the drawing than in step 2, you must make double or than in step 2, you must make double or triple bonds. If you have less electrons in the triple bonds. If you have less electrons in the drawing than in step 2, you made a mistake!drawing than in step 2, you made a mistake!

H•• H

H

N

Carbon Dioxide, COCarbon Dioxide, CO22Carbon Dioxide, COCarbon Dioxide, CO22

1. Central atom = 1. Central atom =

2. Valence electrons =2. Valence electrons =

3. Form bonds.3. Form bonds.

O OC4. Place lone pairs on outer atoms.4. Place lone pairs on outer atoms.

This leaves 12 electrons (6 pair).This leaves 12 electrons (6 pair).

5. Check to see that all atoms have 8 electrons 5. Check to see that all atoms have 8 electrons around it except for H, which can have 2.around it except for H, which can have 2.

C 4 e-C 4 e-O 6 e- X 2 = 12 e-O 6 e- X 2 = 12 e-Total: 16 valence electronsTotal: 16 valence electrons

Carbon Dioxide, COCarbon Dioxide, CO22Carbon Dioxide, COCarbon Dioxide, CO22

••O OC

•• ••

••••••

••O OC

•• ••

••••••

••O OC

•• ••

••

••O OC

•• ••

••

6. There are too many electrons in our drawing. We 6. There are too many electrons in our drawing. We must form DOUBLE BONDS between C and O. must form DOUBLE BONDS between C and O. Instead of sharing only 1 pair, a double bond shares 2 Instead of sharing only 1 pair, a double bond shares 2 pairs. So one pair is taken away from each atom and pairs. So one pair is taken away from each atom and replaced with another bond.replaced with another bond.

C 4 e-C 4 e-O 6 e- X 2 = 12 e-O 6 e- X 2 = 12 e-Total: 16 valence electronsTotal: 16 valence electrons

How many are in the drawing?How many are in the drawing?

Lewis-dot Structure: NaCl Lewis-dot Structure: NaCl

Na Na → 1 valence e→ 1 valence e--

Cl Cl → 7 valence e→ 7 valence e-- s s

Total = 8 e- sTotal = 8 e- s

Na Cl

Lewis-dot Structure: NaCl Lewis-dot Structure: NaCl

Na Na → 1 valence e→ 1 valence e--

Cl Cl → 7 valence e→ 7 valence e-- s s

Total = 8 e- sTotal = 8 e- s

Na Cl

Lewis-dot Structure: NaCl Lewis-dot Structure: NaCl

Na Na → 1 valence e→ 1 valence e--

Cl Cl → 7 valence e→ 7 valence e-- s s

Total = 8 e- sTotal = 8 e- s

Na ClXIt must be an Ionic Bond!It must be an Ionic Bond!

Ionic bonding: NaCl Ionic bonding: NaCl

Cl –Na+Na Cl

Ionic bonding: LiIonic bonding: Li22OO

O 2–OLi

Li Li +

Li +

Carbon Monoxide, COCarbon Monoxide, COCarbon Monoxide, COCarbon Monoxide, CO

1. Valence electrons =1. Valence electrons =

2. Form bonds.2. Form bonds.C 4 e-C 4 e-O 6 e-O 6 e-Total: 10 valence electronsTotal: 10 valence electrons

Nitrous Oxide, NNitrous Oxide, N22OONitrous Oxide, NNitrous Oxide, N22OO

1. Valence electrons =1. Valence electrons =

2. Form bonds.2. Form bonds.N 5 e- X 2 = 10 e-N 5 e- X 2 = 10 e-

O 6 e-O 6 e-Total: 16 valence electronsTotal: 16 valence electrons