1. Drill: Ionic bonding Objective:
Swbat: Demonstrate sharing of electrons in order to model covalent bonding by combining Lewis dot diagrams.

2. SAT ENRICHMENT: The bonds in BaO are best described as….
Covalent, because valence electrons are shared.
Covalent, because valence electrons are transferred.
Ionic, because valence electrons are shared.
Ionic, because valence electrons are transferred.
Metallic, because valence electrons exist in a “mobile sea”.

3. ENGAGEMENT:
Safari Montage Video: Properties of Compounds: Covalent Bonding:

4. Covalent Bonding WebQuest!
Covalent Bonding Webquest (SR.CHEMBOND.02A)
30 min

5. Covalent Compounds Covalent Bonds Two nonmetals
Weaker than ionic bonds
Electrons shared, not transferred

6. Covalent Compounds → Cl + F Cl F → S + O S O
Example: Chlorine and fluorine (ClF)
Problem 1: Sulfur and oxygen (SO) • • • • ◙ ◙ ◙ ◙ • • → • • Cl + F ◙ Cl F ◙ • • ◙ ◙ ◙ ◙ • • • • ◙ ◙ ◙ ◙ • • • • ◙ • • → • • S + O ◙ S ◙ O ◙ • • • ◙ ◙ ◙ ◙ • ◙ ◙ ◙ ◙

7. Covalent Compounds → Br + Se + Br Se Br Br → C + O C O
Problem 2: Selenium and bromine (SeBr2)
Problem 3: Carbon and oxygen (CO) • • • • • • • ◙ ◙ • ◙ ◙ → • Br + ◙ Se ◙ + Br ◙ Se ◙ Br • • • • • • ◙ ◙ • • ◙ • • • • • ◙ • • Br • • • • • ◙ ◙ → • • C + ◙ O ◙ C ◙ ◙ O ◙ • • • • ◙ ◙ ◙ ◙ • ◙

8. Bond Polarity
If there is an unequal sharing of electrons, the bonding electrons spend more time near the atom with the highest electronegativity causing it to obtain a slightly negative charge.
The atom with the lower electronegativity acquires a slightly positive charge.

9. Electronegativities Electronegativities for the first six periods
The difference between two elements’ electronegativities indicates the degree of electron sharing (or transfer) in a chemical bond
The closer the electronegativity, the more equally the electrons are shared. H
2.1 Li
1.0 Be
1.5 B
2.0 C
2.5 N
3.0 O
3.5 F
4.0 Na
0.9 Mg
1.2 Al Si
1.8 P S Cl K
0.8 Ca Sc
1.3 Ti V
1.6 Cr Mn Fe Co
1.9 Ni Cu Zn Ga Ge As Se
2.4 Br
2.8 Rb Sr Y Zr
1.4 Nb Mo Tc Ru
2.2 Rh Pd Ag Cd
1.7 In Sn Sb Te I Cs
0.7 Ba La Hf Ta W Re Os Ir Pt Au Hg Tl Pb Bi Po At

10. Nonpolar Covalent Bond- Polar Covalent Bond
Polar or Nonpolar?
Nonpolar Covalent Bond-
Electronegativity difference ≤ 0.4
Polar Covalent Bond
0.4 < Electronegativity difference < 1.7

11. Predicting Bond Type
Example 1: OF2
EN of O = 3.5
EN of F = 4.0
4.0 – 3.5 = 0.5
0.5 is less than 1.7 but greater than 0.4, so the bond is polar covalent.

12. Example 2: Cl2 Predicting Bond Type EN of Cl = 3.0 3.0 – 3.0 = 0.0
0 ≤ 0.4, so the bond is nonpolar covalent.

13. Example 3: CS2 C: 2.5 S: 2.5 2.5 – 2.5 = 0.0 Nonpolar Covalent
Predicting Bond Type
Example 3: CS2
C: 2.5
S: 2.5
2.5 – 2.5 = 0.0
Nonpolar Covalent

14. Example 4: NH3 N: 3.0 H: 2.1 3.0 – 2.1 = 0.9 Polar Covalent
Predicting Bond Type
Example 4: NH3
N: 3.0
H: 2.1
3.0 – 2.1 = 0.9
Polar Covalent

15. Special Case: Polar Covalent
Polar covalent molecules have a dipole
Molecules with dipoles have partially charged ends
For water:
Oxygen has an electronegativity of 3.5
Hydrogen has an electronegativity of 2.1
Because oxygen is more electronegative, it will be the negative end of the dipole
Because hydrogen is less electronegative, it will be the positive end of the dipole ◙ ◙ ◙ O ◙ H •
Negative ◙ • ◙ H
Positive

16. Bonding
Complete bonding worksheet
10 min

17. Summary: Did we accomplish the objective? Explain.
Define a Covalent bond.
What criteria would you use to assess whether a bond is ionic or covalent?
What criteria would you use to assess whether a bond is polar or nonpolar?

18. Homework:
Chromatography Pre-Lab
(NO HOMEWORK PASSES MAY BE USED)

19. Drill: Quiz: Covalent Bonding (5 min) Objective:
Swbat: Demonstrate sharing of electrons in order to model covalent bonding by combining Lewis dot diagrams.

20. SAT ENRICHMENT:
Generally… valence electrons are needed for atoms to be most stable. 2 6 8 18 32

21. Chromatography Lab
Review Lab procedures.
Chromatography Lab
45 min

22. Exit Ticket & Extension
Covalent Bonding Exit ticket
Extension: Oil and Soap Molecule Simulation:
5 min

23. Summary Did we accomplish the objective? Explain.
Identify the purpose of the chromatography lab.
Explain your chromatography lab results. Which colors were soluble in water?

24. Homework
Instructional Fair Pages 38 and 39!