Which choice represents a pair of resonance structures?
Which choice represents a pair of resonance structures?
:Cl⋅⋅⋅⋅−O⋅⋅⋅⋅−H:Cl⋅⋅⋅⋅−O⋅⋅⋅⋅−H and :Cl⋅⋅⋅⋅−O⋅⋅⋅⋅:−:Cl⋅⋅⋅⋅−O⋅⋅⋅⋅:−
N⋅⋅N⋅⋅≡C−Br⋅⋅⋅⋅:≡C−Br⋅⋅⋅⋅: and C⋅≡N⋅−Br⋅⋅⋅⋅:C⋅≡N⋅−Br⋅⋅⋅⋅:
O⋅⋅⋅⋅=O⋅⋅⋅⋅O⋅⋅⋅⋅=O⋅⋅⋅⋅ and :F⋅⋅⋅⋅−F⋅⋅⋅⋅::F⋅⋅⋅⋅−F⋅⋅⋅⋅:
:O⋅⋅⋅⋅−S⋅⋅⋅=O⋅⋅::O⋅⋅⋅⋅−S⋅⋅⋅=O⋅⋅: and :O⋅⋅=S⋅⋅⋅−O⋅⋅⋅⋅::O⋅⋅=S⋅⋅⋅−O⋅⋅⋅⋅:
The Correct Answer and Explanation is :
The correct answer is:
:Cl⋅⋅⋅⋅−O⋅⋅⋅⋅:−:Cl⋅⋅⋅⋅−O⋅⋅⋅⋅:−
Explanation:
Resonance structures are different ways of representing the same molecule, where the connectivity of atoms remains the same, but the distribution of electrons can vary. The key feature is that the molecules involved in resonance share the same bonding framework but have different electron configurations, often with the delocalization of electrons.
Let’s break down the options:
- :Cl⋅⋅⋅⋅−O⋅⋅⋅⋅:−:Cl⋅⋅⋅⋅−O⋅⋅⋅⋅:−
- This represents a resonance pair. The molecule contains a chlorine (Cl) atom attached to an oxygen atom (O), which is also connected to a hydrogen (H) atom. In resonance, the negative charge on the oxygen can be delocalized to form a different structure, with a negative charge moving between the oxygen and chlorine atoms. This is a classic example of a resonance structure where the positions of the lone pairs and formal charges on atoms change without altering the connectivity of the atoms.
- N⋅⋅N⋅⋅≡C−Br⋅⋅⋅⋅:≡C−Br⋅⋅⋅⋅: and C⋅≡N⋅−Br⋅⋅⋅⋅:C⋅≡N⋅−Br⋅⋅⋅⋅:
- These structures are not resonance pairs. While the bonding is similar, the atoms themselves change places between the two structures. The connectivity of atoms (N, C, Br) is different in these two structures, meaning this is not an example of resonance.
- O⋅⋅⋅⋅=O⋅⋅⋅⋅O⋅⋅⋅⋅=O⋅⋅⋅⋅ and :F⋅⋅⋅⋅−F⋅⋅⋅⋅::F⋅⋅⋅⋅−F⋅⋅⋅⋅:
- The first example is also not resonance because the atoms involved are not in the same bonding framework; there are multiple oxygens and bonds that change places. The second example is not valid either because fluorine atoms are highly electronegative, and this representation does not match a realistic resonance pair for fluorine.
- :O⋅⋅⋅⋅−S⋅⋅⋅=O⋅⋅::O⋅⋅⋅⋅−S⋅⋅⋅=O⋅⋅: and :O⋅⋅=S⋅⋅⋅−O⋅⋅⋅⋅::O⋅⋅=S⋅⋅⋅−O⋅⋅⋅⋅:
- This set also doesn’t represent resonance structures. The bonding and formal charge are not conserved across both examples, so this isn’t a resonance scenario.
In summary, resonance structures must involve atoms that are connected in the same way, with only the arrangement of electrons differing. The first choice correctly represents resonance structures with only electron shifts and formal charge changes without altering the connectivity of the atoms.