1. More Chemical Bonding

2. Metallic Bonding Metals generally have the following properties:
High melting/boiling points
Conduct electricity and heat
Hard and dense
Can be hammered into shapes (malleable)
Can be pulled into wire (ductile)

3. Metallic Bonding The bonds in metals are neither ionic or covalent
Atoms of one metal are surrounded by a sea of electrons which are very mobile and not confined to individual atoms.
This sea of electrons is called the “free-electron model”.

4. Free-Electron Model

6. Intramolecular Bonds - Summary
Bonds within compounds: Intramolecular
Metallic Bonding
m + m
Ionic Bonding
m + nm
Covalent
nm + nm
Nonpolar
Equal sharing
Polar
Unequal sharing

7. Intermolecular Forces
We have been looking at intramolecular forces thus far – how atoms within molecules are held together.
There are also forces that act between molecules:
dipole-dipole attractions
hydrogen bonding

8. Dipole-Dipole Attractions
Are attractions between polar molecules.
The positive end (+) of a polar molecule is attracted to the negative end (-) of an adjacent polar molecule.
These forces are relatively weak.

9. Dipole-Dipole Attractions

10. Hydrogen Bonding
is a strong type of dipole-dipole attraction that exists between molecules having H-F, H-O, and H-N bonds.
Hydrogen bonds play an important role in the structure of the DNA molecule and in many biological proteins.

11. Hydrogen Bonding in Water