Metallic bonds are strong electrostatic interactions that form between
metal atoms and mobile electrons.
LEARNING OBJECTIVE [ edit ]
Describe the electron sea model of metallic bonding.
KEY POINTS [ edit ]
Many of the unique properties of metals can be explained by metallic bonds.
Metallic bonds can occur between different elements to form an alloy.
In contrast to electrons that participate in both ionic andcovalent bonds, electrons that
participate in metallic bonds delocalize, forming a sea of electrons around the positive nuclei of
metals. The availability of "free" electrons contributes to metals being excellent conductors.
TERMS [ edit ]
metallic bond
A chemical bond in which mobile electrons are shared over many nuclei; this leads to electrical
conduction.
electron sea
The body of delocalized electrons that surrounds positive metal ions in metallic bonds.
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Metallic Bonding
Metallic bonds are strong electrostatic interactions that form between metal atoms and
loosely bound electrons. The structure of metallic bonds is very different from that of
covalent and ionic bonds. While ionic bonds join metals to nonmetals, and covalent bonds
join nonmetals to nonmetals, metallic bonds are responsible for the bonding between metal
atoms.
In metallic bonds, the valence electrons from the s and porbitals of the interacting metal
atoms delocalize. That is to say, instead of orbiting their respective metal atoms, they form a
"sea" of electrons that surrounds the positively charged atomic nuclei of the interacting metal
ions. The electrons then move freely throughout the space between the atomic nuclei.
Metallic Bonding: The Electron Sea Model
Positive atomic nuclei surrounded by a sea of delocalized electrons (the black dots).
The characteristics of metallic bonds explain a number of the unique properties of metals:
Metals are good conductors of electricity because the electrons in the electron sea are free
to flow and carry electric current.
Metals are ductile and malleable because local bonds can be easily broken and reformed.
Metals are shiny. Light cannot penetrate their surface; thephotons simply reflect off the
metal surface. However, there is an upper limit to the frequency of light at which the
photons are reflected.
Metallic bonds can occur between different elements, forming an alloy. Aluminum foil
and copper wire are examples of metallic bonding in action .
Metallic Bonds in Aluminum Foil
Take note of the unique metallic properties that aluminum foil exhibits.
Metallic bonds are mediated by strong attractive forces. This property contributes to the low
volatility, high melting andboiling points, and high density of most metals. The group­XII
metals zinc, cadmium, and mercury are exceptions to this rule.