Determine the molecular geometry about each interior atom and draw each molecule. (Skeletal structure is indicated in parentheses.) a. N2 b. N2H2 (HNNH) c. N2H4 (H2NNH2)
The Correct Answer and Explanation is:
. N₂ (Nitrogen Gas)
Molecular Geometry:
- The molecule consists of two nitrogen atoms connected by a triple bond, with no lone pairs on either atom.
- The electron geometry and molecular geometry for N₂ are both linear.
Explanation:
- In N₂, each nitrogen atom has a lone pair and forms a triple bond with the other nitrogen. This results in a linear molecular shape, with bond angles of 180°. Since there are no lone pairs affecting the geometry, the bond angle remains straight.
- The structure of N₂ can be represented as:
N ≡ N (triple bond between the nitrogen atoms).
b. N₂H₂ (Diazene or Hydrazine)
Molecular Geometry:
- In N₂H₂, there are two nitrogen atoms, each bonded to one hydrogen atom, with a single bond between them.
- The molecular geometry about each nitrogen atom is trigonal planar for the central nitrogen atoms.
Explanation:
- The two nitrogen atoms in N₂H₂ are connected by a single bond. Each nitrogen is also bonded to a hydrogen atom. The lone pairs on the nitrogen atoms influence the geometry.
- The trigonal planar arrangement arises because there is one bond between the two nitrogen atoms and each nitrogen has two other groups around it (one hydrogen and one single bond to another nitrogen).
- The bond angles are approximately 120°.
- The skeletal structure for N₂H₂ is:
H-N=N-H
c. N₂H₄ (Hydrazine)
Molecular Geometry:
- N₂H₄ consists of two nitrogen atoms each bonded to two hydrogen atoms, with a single bond between the nitrogen atoms.
- The molecular geometry around each nitrogen is tetrahedral, and the bond angles are approximately 109.5°.
Explanation:
- Each nitrogen atom in N₂H₄ is bonded to two hydrogen atoms and one nitrogen atom, with a lone pair of electrons on each nitrogen.
- The tetrahedral geometry arises from the lone pairs, as they create repulsion with the bonded atoms, pushing them into a tetrahedral arrangement to minimize electron pair repulsion.
- The bond angles are close to the ideal 109.5° for a tetrahedral molecule.
- The skeletal structure for N₂H₄ is:
H₂N-NH₂
Summary of Molecular Geometries:
- N₂: Linear (180° bond angle)
- N₂H₂: Trigonal Planar around the nitrogen atoms (approx. 120° bond angle)
- N₂H₄: Tetrahedral around the nitrogen atoms (109.5° bond angle)
