Show a Lewis structure of an isomer of urea that still has both Ns and the 0 bonded to the C and has formal charges of zero at all atoms

/ Exams & Certification / By

Show a Lewis structure of an isomer of urea that still has both Ns and the 0 bonded to the C and has formal charges of zero at all atoms.

The correct answer and explanation is :

The isomer of urea you are referring to is cyanamide (H2NCN), which is an isomer of urea but with a different bonding arrangement between the nitrogen atoms. Below is the Lewis structure for cyanamide:

H-N=C=N-H

Lewis Structure Explanation:

  1. Valence Electrons Calculation:
  • Carbon (C) has 4 valence electrons.
  • Nitrogen (N) has 5 valence electrons (for each N).
  • Hydrogen (H) has 1 valence electron (for each H).
  • Therefore, for cyanamide (H2NCN), the total number of valence electrons is:
    [
    (2 \times 1) + (2 \times 5) + (1 \times 4) = 2 + 10 + 4 = 16 \text{ valence electrons}.
    ]
  1. Bonding:
  • The carbon atom (C) is the central atom, bonded to two nitrogen atoms (N).
  • Each nitrogen atom is also bonded to a hydrogen atom, forming H-N and N-H bonds.
  • The bonding between carbon and nitrogen in cyanamide is a double bond (C=N). Between the two nitrogen atoms, there is a single bond (N-N).
  1. Formal Charge Considerations:
  • The formal charge is calculated as:
    [
    \text{Formal Charge} = \text{Valence Electrons} – \text{Nonbonding Electrons} – \frac{1}{2} \times \text{Bonding Electrons}
    ]
  • For the carbon atom (C), it forms four bonds (two with N and two with H), satisfying its octet with no lone pairs. Thus, it has a formal charge of 0.
  • The nitrogen atoms (N) are each bonded to one hydrogen atom and either another nitrogen or carbon. Each nitrogen achieves a full octet and has no lone pairs or extra electrons, resulting in a formal charge of 0 for each nitrogen.
  1. Resonance: There are no resonance structures for cyanamide since the bonding arrangement does not allow for multiple valid resonance forms.

Thus, cyanamide (H2NCN) satisfies the condition of having zero formal charges for all atoms while maintaining both nitrogen atoms bonded to carbon. This structure is a valid isomer of urea with a different bonding configuration, and it follows the principle of formal charge neutrality.

Related Posts

Scroll to Top