Write a comprehensive essay discussing Goldschmidt and Paulings ideas on bonding, the importance of ionic size, valence, etc. Generally, you will be discussing Goldschmidts rules of substitution.

When size difference exceeds 30 , one can expect little or no substitution at all ( Mineralogy ' 1997

2 . Ionic Charge and electroneutrality Pauling stressed the importance of valence number of an atom in his rule number 2 known as electrostatic valency principle . A valence number is the number of electrons found on the outermost shell orbital of an atom that has the ability to form bonds (Brescia 144 . According to him , it is critical that the central cation or anion must equal to the valence number of the central anion or cation . Therefore

, it is essential that the proxy cation must have the same valence number to the cation , otherwise substitution may require higher energies that will ultimately result to the termination of substitution ( Atomic Structures of Minerals 2005 . Accordingly , Goldschmidt 's rule number two in ionic substitution states that ions whose charges differ by 1 unit substitute readily for one another if electrical neutrality of crystal is maintained by coupled substitution ( Atomic Structure ' 2008 . Generally , if the difference in charges is greater than one unit , there may be very little or no substitution at all . Furthermore , in Goldschmidt 's rule number 3 if there are two different ions that occupies an atomic site , it would be the ion with the higher ionization potential ( energy needed to remove the outermost electron to produce a cation ) that forms a more stronger bond with anions surrounding it ( Atomic Structure ' 2008

3 . Electronegativity

Electronegativity refers to the ability of an atom to attract electrons towards itself resulting to the formation of an anion after the atom gains an electron (Brescia 155 . In Goldschmidt 's rule number 4 , substitution occurs when proxy element ion has similar electronegativity as the element ion . High difference in electronegativities normally results to a bonds of different character with the...