Questions: Specify the formal charges (both sign and magnitude) on the atoms labelled a-c.

Solution Steps

• For the first molecule (H₃C-C≡N-O):
  • Carbon (C) typically has 4 valence electrons.
  • Nitrogen (N) typically has 5 valence electrons.
  • Oxygen (O) typically has 6 valence electrons.

• Formal charge formula: \( \text{Formal charge} = \text{Valence electrons} - \text{Non-bonding electrons} - \frac{1}{2} \times \text{Bonding electrons} \)

• Valence electrons: 6
• Non-bonding electrons: 6 (3 lone pairs)
• Bonding electrons: 2 (1 single bond with Nitrogen)
• Formal charge: \( 6 - 6 - \frac{1}{2} \times 2 = 6 - 6 - 1 = -1 \)

• Valence electrons: 5
• Non-bonding electrons: 0
• Bonding electrons: 8 (3 bonds with Carbon and 1 bond with Oxygen)
• Formal charge: \( 5 - 0 - \frac{1}{2} \times 8 = 5 - 4 = +1 \)

• Valence electrons: 4
• Non-bonding electrons: 0
• Bonding electrons: 8 (3 bonds with Nitrogen and 1 bond with Hydrogen)
• Formal charge: \( 4 - 0 - \frac{1}{2} \times 8 = 4 - 4 = 0 \)

• For the second molecule (H₂C=N=N):
  • Carbon (C) typically has 4 valence electrons.
  • Nitrogen (N) typically has 5 valence electrons.

• Valence electrons: 4
• Non-bonding electrons: 0
• Bonding electrons: 4 (2 bonds with Hydrogen and 1 double bond with Nitrogen)
• Formal charge: \( 4 - 0 - \frac{1}{2} \times 4 = 4 - 2 = +2 \)

• Valence electrons: 5
• Non-bonding electrons: 2 (1 lone pair)
• Bonding electrons: 6 (1 double bond with Carbon and 1 double bond with Nitrogen)
• Formal charge: \( 5 - 2 - \frac{1}{2} \times 6 = 5 - 2 - 3 = 0 \)

• Valence electrons: 5
• Non-bonding electrons: 4 (2 lone pairs)
• Bonding electrons: 2 (1 double bond with Nitrogen)
• Formal charge: \( 5 - 4 - \frac{1}{2} \times 2 = 5 - 4 - 1 = 0 \)

Final Answer