High School Chemistry : Help with Resonance

Study concepts, example questions & explanations for High School Chemistry

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Example Questions

Example Question #61 : Compounds And Bonding

When will resonance be possible in a molecule?

Possible Answers:

The molecule must have a triple bond adjacent to a single bond

The molecule must contain carbon atoms

The molecule must contain oxygen or nitrogen

The molecule must only contain single bonds 

The molecule must contain a double or triple bond adjacent to a single bond

Correct answer:

The molecule must contain a double or triple bond adjacent to a single bond

Explanation:

Resonance is the movement of electrons from one bond to another. This helps to shift the electron distribution between multiple atoms, creating molecular stability. In order for resonance to occur, there must be a pi bond next to a sigma bond. A pi bond is a double bond or triple bond and a sigma bond is a single bond. During resonance, the electrons from the pi bond move around causing the double (or triple) bond to shift positions. This frequently occurs with oxygen and nitrogen because they have several valence electrons and can readily form pi bonds, but these elements are not required to form resonance structures.

Example Question #62 : Compounds And Bonding

Which of the following best explains the concept of resonance structures?

Possible Answers:

Chemists are unsure of the structures of some molecules, so they use resonance structures to model several possibilities at once

Certain molecules exist in nature whose structures may have two or more different forms based on the instantaneous locations of electrons within the molecule

Certain molecules exist in nature whose structures may have two or more different forms based on the locations of atoms within the molecule

Certain elements exist in nature in several different isotopes

Correct answer:

Certain molecules exist in nature whose structures may have two or more different forms based on the instantaneous locations of electrons within the molecule

Explanation:

Resonance structures are a way of describing the different possible locations of delocalized electrons within a molecule. Although a molecule might have several correct resonance forms, often, one is more stable than the others. Molecules whose structures differ in the locations of atoms are called isomers. 

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