Calculate the oxidation number of sulphur, chromium, and nitrogen in `H_(2)SO_(5), Cr_(2)O_(7)^(2-)` and `NO_(3)^(Θ)`. Suggest the structure of these compounds. Count for the fallacy.

Explanation

(i) `H_2SO_5` By conventional method
`overset(+1)(H_2)overset(x)(S)overset(-2)O_5`
`2(+1) +x +5 (-2) = 0 " or "x =+8`
This is not possible because S cannot have O. N. more than 6. The fallacy is overcomed if we calculate its O.N from its stucture as :
`H-O-overset(O)overset(||)underset(O)underset(||)S-O-O-H`
`underset(("for H"))(2xx(1+))+underset(("for S"))x+underset(("for O-O"))(2-(1))+underset(("for other O atom"))(3xx(-2)=0)`
or x = + 6
(ii) `Cr_2O_7^(2-)`
2x + 7(-2)=-2
`2x = 12 " ":. x = +6`
This is correct and there is no fallacy.
(iii) `NO_3^(-)` By conventional method,
`x+3(-2)=-1 " or "x =+5`
From the structure ,

`underset(("for " O^(-)))x+underset(("for =O) (for "rarrO))(1(-1)+1(-2)=0)" or "x = +5`
Hence , there is no fallacy about O.N. of N in `NO_3^(-)` as +5 whethere we calculate by conventional method or by chemical bonding :