Question

What is the oxidation number of `"H"_2"O"` ?

Answer 1

Well, oxidation number is an atomic property, i.e. a property of the atoms within a molecule....

Explanation:

And since water is a neutral molecule, the SUM of the oxidation numbers of hydrogen, and oxygen WITHIN THE MOLECULE must be ZERO....

And thus within water...

`H_"oxidation number"=+I`...

`O_"oxidation number"=-II`...

And `2xxH_"oxidation number"+O_"oxidation number"=0`...as required...

Of course, as the ELEMENTS, NEITHER oxygen nor hydrogen are conceived to have been reduced or oxidized...and their oxidation numbers are ZERO....