1. Chapter 8
Bonding

2. Lewis Structures Diagram that shows Simple way of showing electrons
American chemist Gilbert N. Lewis
Dots =
Paired dots =
Simple way of showing electrons
Most reactions involve only

3. Lewis Structures When drawing:
Use electron configuration
Move in clockwise direction…
“12” = s orbital
“3, 6, 9” = p orbitals – fill each with ONE electron before filling with pairs…
Just like orbital filling diagram…
Examples: draw Lewis Structures of B, N, F, Ne

4. The Ionic Bond Ionic bond: Transfer of electrons from Ions form with
Attraction between electrostatic charges is a strong force which holds atoms together

5. The Ionic Bond
NOT A
Bond not just between (for example) one sodium and one chloride

6. The Ionic Bond
Typically
Metals usually
Nonmetals usually

7. Predicting Formulas of Ionic Compounds
In almost all stable chemical compounds of representative elements, each atom attains a
This concept forms the basis for our understanding of chemical bonding.

8. Predicting Formulas of Ionic Compounds
How many electrons must be gained or lost to achieve noble gas configuration?
Ba must lose
Forms the ion
S must gain
So…must be ratio of

9. Predicting Formulas of Ionic Compounds
Elements in a family usually form compounds with the same atomic ratios
Because they have the same number of valence electrons
Must gain or lose the same number of electrons
See table 11.4 pg 233

10. Predicting Formulas of Ionic Compounds
The formula for sodium oxide is Na2O. Predict the formula for
Sodium sulfide

11. Predicting Formulas of Ionic Compounds
Rubidium Oxide
Rubidium
Oxygen
So…formula must be
This makes sense b/c rubidium is in same family as sodium

12. The Covalent Bond A pair of Most common type of bond Stronger than
Electron orbital expands to include both nuclei
most often found between
Negative charges allow positive nuclei to be drawn close to each other

13. The Covalent Bond Atoms may share more than one pair of electrons
Double bond –
Triple bond –
Multiple bonds are
Covalent bonding between identical atoms means electrons are shared
Covalent bonding between different atoms leads to

14. Electronegativity
The attractive force that an atom of an element has for
Atoms have different electronegativities
Electrons will spend more time near atom with
So…one atom assumes a partial
The other assumes a partial

15. Electronegativity Electronegativity trends and periodic table
See table 11.5 page 237
Generally increases from
Decreases
Highest is
Lowest is

16. Electronegativity
Polarity is determined by difference in electronegativity
Nonpolar covalent
Polar covalent
Ionic compound

17. Electronegativity If the electronegativity difference is greater than
Above
Below

18. Electronegativity Polar bonds form between two atoms
Molecules can also be polar or nonpolar
Dipole
Polar
Nonpolar

19. Lewis Structures of Compounds
Convenient way of showing ionic or covalent bonds
Usually the single atom in a formula is the central atom

20. The Ionic Bond
LEWIS STRUCTURES of ionic bonds

21. The Covalent Bond LEWIS STRUCTURES of covalent bonds
Use dashes instead of dots…

22. The Covalent Bond

23. Lewis Structures of Compounds
Obtain the total number of valence electrons
Add the valance electrons of all atoms
Ionic – add one electron for each negative charge and subtract one electron for each positive charge

24. Lewis Structures of Compounds
Write the skeletal arrangement of the atoms and connect with a single covalent vond
Subtract two electrons for each single bond
This gives you the net number of electrons available for completing the structure

25. Lewis Structures of Compounds
Distribute pairs of electrons around each atom to give each atom a noble gas structure
If there are not enough electrons then try to form double and triple bonds

26. Lewis Structures of Compounds
Write the Lewis Structure for methane CH4

27. Lewis Structures of Compounds
Carbon Dioxide, CO2

28. Complex Lewis Structures
Some molecules and polyatomic ions have strange behaviors…
No single Lewis structure is consistent
If multiple structures are possible the molecule shows

29. Complex Lewis Structures
Carbonate ion, CO32-

30. Compounds Containing Polyatomic Ions
Behaves as a single unit in many chemical reactions
Sodium carbonate (Na2CO3)