[fatghost13]

There are some questions that need to help 
Refer to the attached
I would like to know which oxygen atom(s) should be electrophilic and should will be nucleophilic.
In the meantime , why one of these labeled electrophilic cannot participate in actual reaction?

[Dan]

You must show you have attempted the question, this is a Forum Rule.

[Arkcon]

Also, where did you get this diagram?   You see, the last time you asked about ozone, here: http://www.chemicalforums.com/index.php?topic=68279.msg246076#msg246076, I linked you to WIkipedia, here:  http://en.wikipedia.org/wiki/Ozone#Structure  Which doesn't have the alternate resonance structures your image has.

[Sossy]

Note that resonance structures III and IV do not satisfy the octet rule, and are therefore rejected.

Note also that the two peripheral O atoms are equivalent, and since the central oxygen bears the positive formal charge in the two resonance structure, we conclude that the central oxygen is electrophilic and the other two oxygen atoms are nucleophilic.