December 03, 2013
Examples of Metals
http://www.ndt-ed.org/EducationResources/CommunityCollege/Materials/Introduction/metals.htm
http://commons.wikimedia.org/wiki/File:Native_gold_nuggets.jpg
December 03, 2013
Metallic Bonds
• In metal atoms, valence electrons are not held
tightly to any nuclei
• They can move easily from one atom to another
and are called delocalized electrons
*Metallic bond: Metal nuclei are attracted to
delocalized electrons
http://commons.wikimedia.org/wiki/File:Nuvola_di_elettroni.svg
December 03, 2013
Metallic Bonds
• Metals achieve octet by sharing the electrons in its
outer shell with multiple other atoms
• For example, in Sodium (Na), the 3s orbitals of
each sodium atom overlaps the 3s orbitals of 8
other atoms
http://www.chemguide.co.uk/atoms/bonding/metallic.html
December 03, 2013
Metallic Bonds
• Electron sea model: All metal atoms in a metallic
solid contribute their valence electrons to form a
"sea" of electrons
December 03, 2013
Properties of metals:
1.
2.
3.
High melting point and boiling point
Malleable and ductile
Good conductors of heat and electricity
December 03, 2013
Melting and Boiling Point
• Metallic bonds are strong
• Metallic solids have moderately high melting point:
> Can vary: Hg (Mercury) is a liquid at room
temperature
> Most metals are solids at room temperature
• Metallic solids have high boiling point
December 03, 2013
Malleable and Ductile
Malleable: Can hammer into flat sheets
Ductile: Can be pulled into a thin wire
The electrons are mobile (remember sea of
electrons!) so you can push/pull the atoms out of
position without breaking the bonds.
https://www.uwgb.edu/dutchs/EarthSC202Notes/minerals.htm
December 03, 2013
Good conductors of heat and electricity
Conducting electricity: remember, you need charged
particles that can move.
• The delocalized electrons are free to move when an
electric current is applied.
Conducting heat: delocalized electrons can move
heat faster
https://www.uwgb.edu/dutchs/EarthSC202Notes/minerals.htm
December 03, 2013
Metallic bond strength
• Metallic bonds are relatively strong: nuclei of metals
are attracted to delocalized electrons
• Bond strength depends on the number of
delocalized electrons.
> More delocalized electrons = stronger bond
> transition metals have many delocalized
electrons (valence electrons + d sublevel
electrons): Very strong bonds, high melting
point
Which metal would you expect to have a higher
boiling point: Na or Mg?
Na: 884ºC
Mg: 1090ºC
December 03, 2013
In the lab, how could you determine if a solid has an
ionic bond or a metallic bond?