Resonance Structures and Formal Charges

The video tutorial explains how to determine which resonance structure of the thiocyanate ion contributes most to the resonance hybrid. It introduces the concept of formal charges and electronegativity, and outlines two key principles: minimizing formal charges on individual atoms and placing negative charges on the most electronegative atoms. The instructor demonstrates how to calculate formal charges for each resonance structure and evaluates them based on these principles, concluding which structure is most significant.

What is the main goal when determining which resonance structure contributes most to the thiocyanate ion's resonance hybrid?

• Maximizing the number of resonance structures

• Minimizing the formal charges on individual atoms

• Ensuring all atoms have the same electronegativity

• Maximizing the total charge of the ion

Why is electronegativity important when evaluating resonance structures?

• It is used to calculate the total number of electrons

• It indicates where negative formal charges should ideally be placed

• It ensures that all atoms have equal charges

• It helps determine the overall charge of the ion

In the first resonance structure, what is the formal charge on the nitrogen atom?

• +1

• -1

• -2

• 0

How many valence electrons does a neutral sulfur atom typically have?

• 6

• 4

• 7

• 5

In the second resonance structure, what is the formal charge on the sulfur atom?

• 0

• -2

• -1

• +1

Which atom in the second resonance structure has a negative formal charge?

• Oxygen

• Carbon

• Sulfur

• Nitrogen

In the third resonance structure, what is the formal charge on the sulfur atom?

• -2

• 0

• +1

• -1

Which resonance structure is determined to contribute most to the resonance hybrid of thiocyanate?

• First structure

• Second structure

• Third structure

• All contribute equally

What is the formal charge on the carbon atom in all resonance structures?

• -2

• +1

• -1

• 0

Why is the second resonance structure preferred over the third?

• It has fewer atoms with non-zero formal charges

• The negative charge is on a more electronegative atom

• It has more resonance structures

• It has a higher total charge