Re: does the sharing of electrons between atoms falls on a continuum

This is a very complex area of chemistry.  However,  as you know, there 
are ionic compounds such as sodium chloride where the bonding electrons 
are held closely to the chlorine atom.  The sodium is therefore positively 
charged and the chlorine negatively charged.  This is therefore 
predominantly ionic in character.

At the other extreme there are covalent compounds, for example the 
hydrogen molecule, in which the bonding electrons are shared equally 
between the two atoms.  Diatomic molecules are therefore totally covalent. 

In between these two extremes there will be a whole range of molecules in 
which the constituent atoms have varying electronegativities.  A 
convenient way of defining the ionic character of a molecule is known as 
the Fractional Ionic Character or FIC.   Calculations of this parameter 
depend upon the differences in electronegativity of the atoms within the 
molecule.  I am not going to go into the maths, but an excellent text book 
is Coulson's Valance by Roy McWeeny, Oxford University Press, 1979 (There 
may be later editions)  ISBN 0-19-855144-4.

I also attach some useful web sites.
 http://www.newi.ac.uk/buckleyc/bonding.htm http://library.thinkquest.org/10429/high/bonding/bonding.htm http://www.comptons.com/encyclopedia/ARTICLES/0100/01239552_A.html

I hope that this helps.


Steve Lancaster.