1. Covalent Bonding

2. Review
Reactivity
Stability
Chemical bond
Lewis dot symbol

3. Covalent bond
Bond in which two or more valence electrons are shared by two atoms
Occurs with elements close to each other on the periodic table
Between a nonmetal and a nonmetal
Ex: H2O, NH3 (ammonia), CH4 (methane)
What types of atoms are H and O (metal / nonmetal / semimetal) ?
A covalent bond forms between what kinds of atoms?

4. 3 Bond Types Single Covalent Bond Double Covalent Bond
Triple Covalent Bond

5. Single Covalent Bonds Each atom shares one pair of electrons
Total of 2 electrons shared
H—H
Lewis Structure

6. Double Covalent Bonds O2 Each atom shares two pairs of electrons
Total of 4 electrons shared O2
Lewis Structure
Label bonding electrons and lone pairs
Oxygen molecule

7. Triple Covalent Bond N2 Each atom shares three pairs of electrons
Total of 6 electrons shared
Lewis Structure N2
Nitrogen molecule

8. Bond Length

9. Bond Lengths
Triple bond < Double Bond < Single Bond

10. Bond Strength Bond Strengths
Triple bond > Double Bond > Single Bond
**Size: the smaller the atom, the stronger the bond (the further away from the nucleus the bonding electrons are, the more shielding there is making it easier to break the bond)
Name the covalent bonds in order of decreasing bond strength.

11. Electronegativity

12. Electronegativity
Ability of an atom to attract towards itself electrons in a chemical bond

13. *video

14. Most electronegative element!
Trend

15. Covalent Bond nonpolar polar H—H H—Cl equal sharing of electrons
Electron density is symmetrical
Unequal sharing of electrons
Electron density is asymmetrical (greater in one region)
H—H
H—Cl

16. Dipole moment e- poor e- rich F H d+ d- H F electron rich region
electron poor
region F H H F d+ d-
BONDS, NOT MOLECULE!!!

17. Classification of bonds by difference in electronegativity
Bond Type
Nonpolar Covalent
0 < and < 2
Polar Covalent
 2
Ionic
Increasing difference in electronegativity
Covalent
share e-
Polar Covalent
partial transfer of e-
Ionic
transfer e-

18. For each bond, indicate the shift in electron density.

19. Practice
Which of the following bonds is nonpolar covalent, which is polar covalent, and which is ionic?
The bond in CsCl
The bond in H2S
The NN bond in H2NNH2

20. Substance Molecule Compound
Two or more atoms chemically bonded together
Two or more elements chemically bonded together

21. Molecules
Diatomic
HCl CO

22. Memorize Diatomic Elements
elements that exist as two
H2, O2, N2, Cl2, Br2, I2, F2
HONClBrIF
“Magnificent 7”
Unpack the title (di / atomic / molecule  2 / atoms / sharing electrons)
**pronounced molecular hydrogen, molecular oxygen…
Diatomic molecules with identical atoms are homonuclear diatomic molecules.

23. Molecules
Polyatomic O3
C6H12O6
CO2
NH3

24. Compound Molecular C6H12O6 C2H5OH CO Binary Molecular Compound HCl CO2
NH3
CO2
Binary Molecular Compound

25. Intermolecular forces
Attractive forces between molecules
3 types:
London dispersion
Dipole-dipole
Hydrogen bond

26. London dispersion
Attractive forces between atoms or nonpolar molecules that arise as a result of temporary dipoles induced by the atom or molecules movement
Usually increase with molar mass
weakest

27. Dipole-dipole
Attractive forces between polar molecules due to their shift in electron density within their molecule
Orientation of Polar Molecules in a Solid

28. Hydrogen Bond
Special dipole-dipole interaction between the hydrogen atom in a polar N-H, O-H, or F-H bond and and electronegative O, N, F atom
strongest
A & B are N, O, or F A H … B or

29. Total Attraction Hydrogen bond Dipole-dipole Dispersion
premium
Hydrogen bond
Dipole-dipole
Dispersion
*Like different TV channel packages
basic

30. Molecular Compound Properties
Tend to be soft solids, liquids, or gases at room temperature
Low melting and boiling points
Poor conductors of heat and electricity
Non-electrolytes

31. A Lewis structure is a model that shows bonding electrons as lines and nonbonding electrons (lone pairs) as dots.
7e-
7e-
8e-
8e- F F + F
single covalent bond
lone pairs
lone pairs F
Lewis structure of F2
lone pairs
lone pairs F
single covalent bond

32. Lewis structure of water
single covalent bonds
2e-
8e-
2e- H + O + H O H or
Double bond – two atoms share two pairs of electrons
8e-
8e-
8e- O C or O C
double bonds
Triple bond – two atoms share three pairs of electrons
8e- N
8e- or N
triple bond