1. Bonding continued

2. Types of Chemical Bonds
Covalent (molecular) bond – results from the sharing of e- between two atoms (usually done w/ nonmetal atoms)
The e- are not always equally shared (like tug of war)

3. Covalent Bonds
Bonds between 2 unlike atoms are never completely covalent
Non-polar covalent – e- are shared equally ( which only happens between two identical atoms)
Polar covalent – e- are not equally shared (due to differences in electronegativity)

4. Determining Bond Type…
Using Periodic Table
Metal Element (left of staircase) + Nonmetal Element (right of staircase)
Ionic Bond
Two Nonmetal Elements (right of staircase)
Covalent Bond

5. Determining Bond Type…
Using Electronegativity Values
Page 161 has a EN chart
Determine the EN difference between the two elements in the bond
Go to page 176 and find the chart of bond types. Use the EN difference to determine type of bond (greater difference = more ionic character).
Nonpolar covalent: difference of 0 to 0.3
Polar covalent: difference of 0.3 to 1.7
Ionic: difference of 1.7 to 4.0

6. Determining Bond Type…
Using Observed Properties from Lab Activity
Conducts electricity while dry
Metallic bonding (valence electrons are free to move from one atom to another)
Dissolves in water
Rule for dissolving is “like dissolves like”
Compounds with either polar covalent bonds or ionic bonds (which are very polar bonds) may dissolve because water has polar covalent bonds

7. Determining Bond Type…
Using Observed Properties from Lab Activity
Conducts electricity while dissolved in H2O
Ionic bonds
Dissolving ionic compounds allows ions to separate and this lets electric current flow from one ion to the next

8. Polar Molecules
Molecules with ends

9. Polar Bonds
When the atoms in a bond are the same, the electrons are shared equally.
This is a nonpolar covalent bond.
When two different atoms are connected, the electrons are
not shared equally.
This is a polar covalent bond.

10. How to show a bond is polar
Isn’t a whole charge just a partial charge
d+ means a partially positive
d- means a partially negative
The Cl pulls harder on the electrons
The electrons spend more time near the Cl d+ d- H Cl

11. Dipole interactions
Occur when polar molecules are attracted to each other.
Slightly stronger than dispersion forces.
Opposites attract but not completely hooked like in ionic solids.

12. Dipole interactions H F d+ d- H F d+ d-
Occur when polar molecules are attracted to each other.
Slightly stronger than dispersion forces.
Opposites attract but not completely hooked like in ionic solids.
H F
d+ d-
H F
d+ d-

13. + - + -

14. Hydrogen Bonding H O d+ d- H O d+ d-

15. - + H - F H - F H - F H - F H - F H - F H - F H - F d+ d- d+ d- d+ d-

16. Electronegativity
A measure of how strongly the atoms attract electrons in a bond.
The bigger the electronegativity difference the more polar the bond.
Use table 12-3 Pg. 285
Covalent nonpolar
Covalent moderately polar
Covalent polar
>2.0 Ionic