Why are singular atoms harmful?

Why would a single oxygen atom be so devastating?
(example: bursting into flames if the atmosphere was filled with single oxygen atoms rather than oxygen molecules, etc.)

The singular oxygen atom is a so called 'free radical', and you can imagine its chemistry that is similar to that of the H2O2 (hydrogene-peroxide) known to be harmful since very oxidatve. If you are curious of the biology of the free radicals you may start from here:
****
http://en.wikipedia.org/wiki/Radical_(chemistry)

Sorry, it is difficult to add an URL to this site, so search Google for
> 'free radicals' wikipedia <
***http://en.wikipedia.org/wiki/Radical_%28chemistry%29

Remember that all atoms are striving to achieve the stability of noble gases I.e. an even numbered electron structure with (2 or 8 etc. electrons), and the quest for finding a like atom with which to bond uses lots of energy. Stability in gases happens when the atoms come together and a certain sense form a covalent (as opposed to an ionic) bond. Hope this is not too technical for you

0

simple words, the less atoms or 'stabilty' the more /faster it moves. Making it highly reactive.