Monday, January 30, 2012

Metallic Bonding

Metals do not form ionic bonds with each other. An aluminum atom, for example, has three valence electrons. It cannot form a bond with another aluminum atom. If one aluminum atom gives up its three valence electrons to another atom, it would have six valence electrons and not be stable. If an aluminum atom gave up its three valence electrons to two other atoms, there would still not be enough electrons to make them stable. Metals also do not form covalent bonds. Metals usually only have one two or three valence electrons with which to make the atoms stable.

How, then, do metals form bonds? The best theory so far seems to be the free electron theory. According to this theory, thousands of atoms join together. The electrons of these atoms move around freely to form stable atoms. This theory is called metallic bonding. It also explains why metals conduct electricity so well. The free movement of the electrons is what helps conduct electricity and give metal its shiny appearance.

Wednesday, January 25, 2012


There are two types of bonding in atoms - ionic and covalent.

Ionic bonds are when two elements join and exchange electrons. They usually form when a metal and a nonmetal bind together. Ionic bonds are responsible for salt, a mixture of chlorine and sodium, or copper fluoride. Ionic bonds tend to form crystals. They have high melting points. They are hard and brittle, dissolving in water, and conduct electricity when dissolved. Ionic bonds prefer to have eight valence electrons, to satisfy the octet rule. The octet rule states that atoms want to have eight valence electrons. When they do, they are at their most stable. Ionic bonds are like Lego sculptures. If you hit them, your hand will just bounce off because they're tightly packed. Your hand might also hurt, too, depending on how hard you hit it.

Covalent compounds are different. They are usually formed when two nonmetals bind together. Covalent bonds are different because they share electrons, not exchange them. Covalent compounds are things like carbohydrates, proteins and water. They are strong but flexible. If you hit a covalent compound, it would be less like hitting a Lego sculpture, and more like hitting a ball pit. They have low melting points, compared to ionic compounds, and don't easily dissolve in water.