[Calypso]

This really isn't a homework question just more of a general..."I need more of an explanation" question hehe.  I'm having some difficulty with polar and purely covalents.  I can do Lewis Structures perfectly fine but figuring out how to classify them as either purely or polar has me running in circles as of right now.  I was wondering if any of you knowledgeable  chemistry whizs could give me a hand  

[mike]

What is "purely"? Do you mean the difference between covalent and polar covalent? In general when there is a large difference in electronegativity between two atoms they will form an ionic bond. When the electronegativities are similar they will form a covalent bond. When there is some difference in electronegativity but not a lot then they will form a polar covalent bond. Remember that covalent bonds occur when atoms share electrons fairly equally while ionic bonds are formed between ions that would prefer to retain or donate electrons.

[Calypso]

Oh whoops I am sorry, my chemistry book refers to them as purely covalents...o_O.  Thank you for the much needed explanation!

[arnyk]

A purely or "truly" covalent bond would be when the electronegativity difference is zero.  So when would that occur?