If you have already learned about covalent and ionic bonding in metallic bonds, you know that these bonds occur between two atoms. When two atoms share electrons, they form a covalent bond. When one atom takes an electron away from another and the resulting positive and negative ions are attracted to each other, those atoms have formed an ionic bond.
How metallic bonding works?
A metallic bond is pretty different from covalent and ionic bonds, but the goal is the same: to achieve a lower energy state. Instead of a bond between just two atoms, a metallic bonds is a sharing of electrons between many atoms of a metal element.
Take a look at your desk and see if you can find a small piece of metal like a paper clip or a staple. All of the atoms in that small piece of metal are sharing a big pool of valence electrons known as a sea of electrons or delocalized electrons. The big pool is like a free-for-all in that any valence electron can move to any atom within the material.
The metallic bond is not the easiest type of bond to understand, so an analogy might help. Imagine filling your bathtub with golf balls. Fill it right up to the top. The golf balls will arrange themselves in an orderly fashion as they fill the space in the tub. Do you see any spaces between the balls? If you turn on the faucet and plug the drain, the water will fill up those spaces. What you now have is something like metallic bonding. The golf balls are the metal atoms, and the water represents the valence electrons shared by all of the atoms.
Once the valence electrons detach from their original atomic owners and float around in the sea, the metal atoms become positive ions. The result is an orderly structure of positive metal atoms surrounded by a sea of negative electrons that hold the ions together like glue.
The composition of metals in metallic bonding
Metals are the only substances that use metallic bonds among their atoms. While many elements are commonly known as metals, including iron, aluminum, gold, silver and nickel, metals include a variety of other elements as well. Most elements are metals, including some such as sodium, radium and calcium, which may not seem very metallic.
Metallic bonds are defined as those in which metals share valence electrons. For example, when sodium metallically bonds with itself, each atom is sharing the electrons in the third orbital with up to eight other atoms. The same thing happens when magnesium or other metals metallically bond to themselves.
Some elements are called transitional metals. These types of elements have even higher melting and boiling temperatures than metals do because they share more valence electrons. While metals share electrons in the third orbital, transition metals share third and fourth orbital electrons.