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When atoms get close enough to interact with each other, there are 3 possible events:
1) They share their valence electrons (ve-) - called covalent bonds (only true "Chemical bond")
2) One atom loses ve- and the other one gains ve- (atoms form ions) - called "Ionic bond"
3) All atoms lose their ve- and the ve- create a "sea of free flowing ve-" or sometimes called "delocalize ve-. We call this a metallic Bond (or simply a metal).
All three events are ruled by the Rule of Eight..
Def: After "bonding" (movement of ve-), all "atoms" need eight ve- around them except H (2ve-), Be (4ve-), B (6ve-) and element in 3rd energy level or greater can have greater than eight.
For the first 2 possible events, how do you know when the atoms share or lose/gain (sometimes called "transferred") ve-. It has to do with the difference between the Electronegativity (ΔEN) of the 2 atoms. The common Rules are:
"Ionic bond" - ΔEN > or = 1.7
"Covalent bond - ΔEN < 1.7
The Covalent bond will be discussed in class.
"Ionic bonds" are placed in quotes because this is a misnomer. A bond by definition is a Chemical bond which means that the ve- are being shared. This is not true for Ionic bonds.
Take notes on or print out the following Powerpoint Presentation that explain "Ionic bonds" in more detailed.
[Ionic Compound Powerpoint Presentation]
The 3rd possible event, Metallic bond, does not depend on ΔEN because all the atoms have low coulombic force (since they are metals) on their valence electrons, so valence electrons can easily be removed from atom to create a "sea of free flowing valence electrons".
Go to Metallic Bond (Metals) for handouts, notes, video and questions about metals.