Q38 / 180 · AIIMS 2004 · Chemistry
The $\mathrm{ONO}$ angle is maximum in
- A$\mathrm{NO}_3^{-}$
- B$\mathrm{NO}_2^{-}$
- C$\mathrm{NO}_2$
- Correct answerD$\mathrm{NO}_2^{+}$.
Solution
The nitrate ion has three resonance structure, with the double bond on a different oxygen for each. In all resonance structures the nitrogen has three bonds, therefore, its hybridisation is $s p^2$. Each of the oxygen atoms also has $s p^2$ hybridisation, since the hybridisation is determined by the resonance structure with the double bond, where the oxygen has a double bond and two lone pairs.
The actual geometry of the polyatomic ion is trigonal planar with bond angles of $120^{\circ}$.
$\mathrm{NO}_2^{-}: 18$ electrons; ideal geometry trigonal planar, $s p^2$ with bond angle of $116^{\circ}$.
$\mathrm{NO}_2: 17$ electrons, ideal geometry trigonal planar; $s p^2$ with bond angle of $134^{\circ}$
$\mathrm{NO}_2^{+}: 16$ electrons; ideal geometry linear ; sp with bond angle of $180^{\circ}$.
$\mathrm{NO}_2^{-}: 18$ electrons; ideal geometry trigonal planar, $s p^2$ with bond angle of $116^{\circ}$.
$\mathrm{NO}_2: 17$ electrons, ideal geometry trigonal planar; $s p^2$ with bond angle of $134^{\circ}$
$\mathrm{NO}_2^{+}: 16$ electrons; ideal geometry linear ; sp with bond angle of $180^{\circ}$.
Hence, the correct answer is option: 'D'.