1. Metallic Bonding

2. Metallic Bond
Occurs between atoms with low electronegativities (metals)
Metal atoms pack close together in 3-D, like oranges in a box.
Creates a close-packed lattice formation

3. This is called a “sea of electrons”
Many metals have an unfilled outer orbital
In an effort to be stable, their outer electrons become delocalized amongst all atoms
No valence electrons belong to one atom, all are shared
The electrons move around throughout the piece of metal.
Metallic bonds are not ions, but nuclei with moving electrons
This is called a “sea of electrons”
Metallic bond animation

4. Electron-Sea Model
Metals can be thought of as cations suspended in “sea” of valence electrons.
Attractions hold electrons near cations, but not so tightly as to impede their flow.
This explains many of the properties of metals, like conductivity of heat and electricity
© 2009, Prentice-Hall, Inc.

5. Physical Properties Conductivity
Delocalized electrons are free to move so when a potential difference is applied they can carry the current (electrons) along
Mobile electrons also mean they can transfer heat well
Ductility
Delocalized electrons allow metals to be stretched into a wire
Luster
The interaction between the mobile electrons with light makes them shiny (luster)

6. Malleability
The electrons are attracted to the nuclei and are moving around constantly.
The layers of the metal atoms can easily slide past each other without the need to break the bonds in the metal
Gold is extremely malleable that 1 gram can be hammered into a sheet that is only 230 atoms thick (70 nm)

7. Malleable +
Force

8. Malleable + + + + + + + + + + + +
Mobile electrons allow atoms to slide by without breaking + + + + + + + + + + + +

10. Melting/Boiling Points
Metals melt at a moderately high temperatures
Metals boil at an extremely high temperature because it requires the cations and its electrons to break away from the others, which takes a lot of energy.
Gallium can melt in your hand at 29.8 oC, but it boils at 2400 oC!

11. Alloys Alloy = mixture of elements with metallic properties
Mixing one metal with other metal(s) or non metal(s) often enhances its properties
Steel is stronger than pure iron because the carbon prevents the delocalized electrons to move so readily.
If too much carbon is added then the metal is brittle.
Alloys are generally less malleable and ductile than the original metal(s)
Some alloys are made by melting and mixing two or more metals
Bronze = copper and zinc
Stainless Steel = iron, carbon, and nickel
Carbide = Tungsten + Carbon