Is NO2 nitrite or nitrate ion?
NO2 is not, by itself, a nitrite or nitrate ion unless a charge is specified; the nitrite ion is NO2− and the nitrate ion is NO3−.
Formulas and names that resolve the ambiguity
| Formula | Name | Charge | Typical context in general chemistry |
|---|---|---|---|
| NO2− | Nitrite ion | \(-1\) | Ionic compounds and aqueous solutions (salts such as sodium nitrite) |
| NO3− | Nitrate ion | \(-1\) | Ionic compounds and aqueous solutions (salts such as potassium nitrate) |
| NO2 | Nitrogen dioxide | \(0\) | Molecular compound (a neutral species; commonly discussed in gas-phase chemistry) |
The suffix -ate indicates the oxygen-richer oxoanion within a related pair or family, while -ite indicates the oxygen-poorer member. For nitrogen oxoanions, nitrate has one more oxygen than nitrite.
Oxidation-state check that distinguishes the ions
Oxidation-state accounting reinforces the distinction. With oxygen taken as \(-2\), nitrogen’s oxidation state differs in nitrite and nitrate.
For nitrite, \(\mathrm{NO_2^-}\): \[ x + 2(-2) = -1 \;\;\Rightarrow\;\; x = +3. \]
For nitrate, \(\mathrm{NO_3^-}\): \[ x + 3(-2) = -1 \;\;\Rightarrow\;\; x = +5. \]
The higher oxidation state in nitrate is consistent with its oxygen-rich formula relative to nitrite.
Visualization of the naming relationship
Concise resolution
NO2− corresponds to nitrite, NO3− corresponds to nitrate, and NO2 without a charge corresponds to nitrogen dioxide.