COMPOUNDS

5.1 - Ionic Bonding

5.1.1 - Ionic Bonding in Sodium Chloride

We can use Lewis Electron Dot Symbols to describe the ionic bonding that is observed in sodium chloride, which is commonly known as table salt. The formation of sodium chloride involves sodium metal, Na and chlorine gas, Cl₂. The reaction can be thought of involving the following simultaneous processes:

1. The Oxidation of Sodium Metal
   Sodium atoms lose its outer-shell electron to become a sodium ion, (i.e. cation). The sodium metal is said to be oxidized.
   The diagram below shows two sodium atoms undergoing oxidation.
   
   
   1. 
      
   2. 
      
      
2. The Reduction of Chlorine Gas
   Recall from section 4.7, chlorine is a diatomic element. The covalently bonded Cl₂ molecule gains two electrons to become two chloride ions, (i.e. anions). Chlorine is said to be reduced.
   
   
   Combining the above oxidation and reduction processess, the overall effect is the transfer of ONE electron from sodium to chlorine.

The oppositely charged sodium and chloride ions attract each other and ionic bonds are formed. In the solid state, each cation is surrounded by anions, and each anion is surrounded by cations. These ions arrange themselves in a 3-dimensional crystal. The simplest ratio of Na⁺ : Cl^- is 1:1. The simplest formula for this ionic compound is NaCl.

Section 6.4
The Ionic Bond ..p124

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