Calculate the oxidation number of

(i) `N` in `NO_(3)^(-)`,
(ii) `P` in `H_(3)P_(2)O_(7)^(-)`,
(iii) `C` in `CO_(3)^(2-)`,
(iv)`Cl` in `ClO_(4)^(-)`
(v)`Cr` in `Cr_(2)^(2-)`
(vi) `Mn` in `MnO_(4)^(-)`
(vii) `Fe` in `[Fe(CN)_(6)]^(4)`

Explanation

To calculate the oxidation numbers for the given elements in the specified compounds, we will follow a systematic approach.

### Step-by-Step Solutions:

**(i) Oxidation number of N in NO₃⁻:**
1. Let the oxidation number of N be \( x \).
2. The oxidation number of O is \(-2\).
3. The formula for the nitrate ion is:
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