Question

For ionic bond why should electropositive element have low ionization potential

Answer 1

Answer:

The Condition required for the formation of an ionic bond between two Elements are: Two elements must be of opposite charge. An element must have its less Ionisation Enthalpy(Cation). Another element must have high negative electron gain enthalpy(Anion).

Answer 2

Answer:

Ionic bonding - Lattice Energy

 

Metals and non-metals interact to form ionic compounds.  An example of this is the reaction between Na and Cl2.  

 

2 Na (s) + Cl2 (g) → 2 NaCl (s)

 

 

It is an extremely exothermic reaction.  A great deal of heat is given off, indicating a large decrease in the PE of the system.  The product, NaCl, is much more stable than the reactants, Na and Cl2.  We can break this reaction down into a few steps, to try to figure out there all of this energy comes from.  We expect a large negative number as the final answer.  

 

First, we need to ionize sodium and chlorine:

 

Ionization Energy          Na → Na+ + e-            +496 kJ/mol     Energy needs to be added in order to remove the electron

Electron Affinity            Cl + e- → Cl-                -349 kJ/mol      Energy is given off when chlorine gains an electron

 

The sum of these two is positive.  There must be some other step involved.  

That step involves assembling the ions into a crystal lattice, so it is called the Lattice Energy.