Question

Write the resonance structures for SO₃ , NO₂ and NO₃^-

Answer 1

Resonance:

Resonance occurs when a molecule or ion can be represented by two or more Lewis structures that differ only in the arrangement of electrons and not in the positions of atoms. The actual structure is a resonance hybrid of all possible structures.

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(a) Resonance structures of SO3

Sulphur trioxide has three equivalent resonance structures. In each structure, one S=O double bond and two S–O single bonds are present. The double bond is delocalised among the three oxygen atoms.

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(b) Resonance structures of NO2

Nitrogen dioxide has two resonance structures. The unpaired electron and the N=O double bond alternate between the two oxygen atoms.

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(c) Resonance structures of NO3 minus ion

The nitrate ion has three equivalent resonance structures. In each structure, one N=O double bond and two N–O single bonds are present. The negative charge is delocalised over the three oxygen atoms.

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Conclusion:

Thus, resonance structures explain the delocalisation of electrons in SO3, NO2, and NO3 minus ion, leading to greater stability of these species.