How can we balance one-half of an oxygen molecule, or any other diatomic, in a chemical reaction?

How can we balance oxygen or any other diatomic molecule with a fractional coefficient in a reaction? I mean, if we can balance oxygen atoms in an odd number what happens to other oxygen atom, and can this sort of reaction even happen?




Whenever a chemical reaction is written with fractional coefficients, implicitly it's meant to be interpreted as the amount of substance *in moles* of each species that is involved. So, it's not really one half of an oxygen *molecule* reacting, but *0.5 moles* of $\ce{O2}$ reacting.


bon's comment is spot-on -- if you are trying to think about a reaction written this way on a molecular level, you need to multiply the reaction through by whatever constant eliminates all the fractions.


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