The Lewis structure of N2H2 shows
A) a nitrogen-nitrogen double bond
B) a nitrogen-nitrogen triple bond
C) each N has one nonbonding electron pair
D) each N has 2 nonbonding electron pairs
E) each H has 1 nonbonding electron pair
The correct answer and explanation is:
The correct answer is:
A) a nitrogen-nitrogen double bond.
Explanation:
The Lewis structure of ( N_2H_2 ) (diazene) reveals that the molecule consists of two nitrogen atoms connected by a double bond and each nitrogen atom bonded to one hydrogen atom. Here’s how this structure is determined and why the correct answer is A:
- Valence Electrons:
- Each nitrogen atom has 5 valence electrons (Group 15 of the periodic table).
- Each hydrogen atom has 1 valence electron (Group 1 of the periodic table).
- Total valence electrons: ( 2 \times 5 + 2 \times 1 = 12 ) electrons.
- Skeletal Structure:
- The two nitrogen atoms are connected by a bond, and each nitrogen atom is attached to a hydrogen atom.
- This basic framework uses 4 electrons (2 for each ( N-H ) bond).
- Distributing Remaining Electrons:
- After forming ( N-H ) bonds, 8 electrons remain.
- A double bond is placed between the two nitrogen atoms, using 4 electrons.
- Each nitrogen atom gets one lone pair of electrons, completing their octets.
- Final Structure:
- The Lewis structure shows:
- A nitrogen-nitrogen double bond.
- Each nitrogen atom has one nonbonding electron pair.
- Each hydrogen atom is bonded to a nitrogen atom and has no lone pairs.
- Why Other Options Are Incorrect:
- ( B ): A nitrogen-nitrogen triple bond is incorrect as there aren’t enough electrons to allow for this while maintaining single bonds with hydrogen.
- ( C ): Each nitrogen has one, not two, nonbonding electron pairs.
- ( D ): Two nonbonding pairs per nitrogen would violate the octet rule.
- ( E ): Hydrogen does not have lone pairs—it forms single bonds.
The nitrogen-nitrogen double bond ensures the structure adheres to the octet rule and balances the electron distribution correctly.