Submitted by Anonymous on Fri, 11/02/2007 - 11:05
Forums
South Pole Ozone Changes

Hi Elke,

I would like to formulate what we discussed earlier regarding the chemistry of natural ozone depletion and UV light. 

When UV light hits the ozone molecule, one oxygen atom is split off. The ozone is formed naturally by combining again with the other two oxygen ozone molecules forming O3. What is the form of energy given off?

Jean-Pierre 

UNIS

HS chemistry teacher 

 

Fri, 11/02/2007 - 12:10

Elke Bergholz

Hi Jean-Pierre, As I told you that my guess was that the form of energy produced in ozone production is heat. I did not think that UV light can be produced by a chemical reaction. You suggested that UV light can also be produced.This is what you wrote in your last email: " Also to answer your question, UV can be produced in a reaction, in fact that the way UV is produced (electronic transition in an atom)" Thanks JPJ
Yes, I agree, UV can be produced within the atom as an electron transition but UV can not be given off by a chemical reaction. As I understand it now: UV light can be produced when an electron of an atom returns from higher atomic shell back to a lower shell once it has been forced to a higher shell, but that is not a chemical reaction. In UV lamps , we take advantage of electron transition.
You were also correct in saying about ozone formation: " ultra-violet radiation from the sun splits oxygen molecules into oxygen atoms which then react with more O2 to form ozone.
Another molecule (M) is needed to absorb some of the huge amount of energy involved in the reaction"
thank you Jean-Pierre form UNIS
I have consulted two chemistry experts and this is what their comments are:
I am quoting here Don Buckley ".. electron transitions do not constitute "chemical reactions", it refers to electrons "jumping" between different states (electron shells) within the atom..a chemical reaction does not occur until an electron "leaves" an atom and is absorbed by another atom ...."
Don Buckley Director Information and Communications Technology The School at Columbia University
Bryan Johnson from the Ozone group at NOAA in Boulder wrote to me the following:
"That is a good question and I believe you are correct. Ozone is very effective at absorbing UV light and breaking into O2 and O. But ozone is reformed again by the O + O2 + M -> O3 + M reaction. M is any other molecule that doesn't dissociate or combine with anything but actually takes the energy of the reaction away when O and O2 recombine, thus creating heat energy. The incoming UV photon therefore is converted to heat in the ozone layer. This web site gives a good explanation."
Thank you Bryan, Don , and Jean-Pierre for the very interesting discussion.

Fri, 01/02/2009 - 22:28

Rishikesh

Respeced Sir /Madam, I am the student of P. G. pharmacy . I want the article of formation of UV light. If u have any imformation or article of such type reply me.
Thank you.
Rishikesh Antre.