General Chemistry/Metallic bonds

Metallic bonds occur among metal atoms. Whereas ionic bonds join metals to non-metals, metallic bonding joins a bulk of metal atoms. A sheet of aluminum foil and a copper wire are both places where you can see metallic bonding in action.

File:Electrona in crystallo fluentia.svg

The "sea of electrons" is free to flow about the crystal of positive metal ions.

When metallic bonds form, the s and p electrons delocalize. Instead of orbiting their atoms, they form a "sea of electrons" surrounding the positive metal ions. The electrons are free to move throughout the resulting network. The delocalized nature of the electrons explains a number of unique characteristics of metals:

Metals are good conductors of electricity	The sea of electrons is free to flow, allowing electrical currents.
Metals are ductile (able to draw into wires) and malleable (able to be hammered into thin sheets)	As the metal is deformed, local bonds are broken but quickly reformed in a new position.
Metals are gray and shiny	Photons (particles of light) cannot penetrate the metal, so they bounce off the sea of electrons.
Gold is yellow and copper is reddish-brown	There is actually an upper limit to the frequency that is reflected. It is too high to be visible in most metals, but not gold and copper.
Metals have very high melting and boiling points	Metallic bonding is very strong, so the atoms are reluctant to break apart into a liquid or gas.

Metallic bonds can occur between different elements. A mixture of two or more metals is called an alloy. Depending on the size of the atoms being mixed, there are two different kinds of alloys that can form:

• Substitutional alloy
  Substitutional alloy
• Interstitial alloy
  Interstitial alloy

The resulting mixture will have a combination of the properties of both metals involved.