Respuesta :
We have the molecular formula:
[tex]NaB(NO_3)_4,[/tex]The first number of oxidation that we need to find is oxygen, which is -2 (you can see it in the periodic table) and multiply that number with the number of oxygen (12 oxygens because 3 x 4 = 12):
[tex]\text{Oxidation of oxygen= -2}\cdot12=-24.[/tex]It is giving us a really low number because is negative, so the other elements must be positive, for example, the unique oxidation number of Na is +1 and the unique number of boron is +3, and based on that we do an algebraic sum to find the oxidation number of N and the result of this sum must be zero:
[tex]-24+3+1=-20.[/tex]N have negative and positive oxidation numbers (2, 3, 4 and 5). In the formula, we have 4 nitrogens and that number is multiplying by anyone of the oxidation numbers. In our case is 5, because 5 x 4 = 20.
The sum of all the number oxidations must be zero:
[tex]Na^{+1}B^{+3}(N^{+5}O^{-2}_3)_4.[/tex]The super indexes indicate the oxidation number of each element.
So the conclusion is the following:
[tex]\text{Oxidation number:}[/tex][tex]Na=\text{ +1, B=+3, N=+5 and O=-16.}[/tex]