Question

Draw the Lewis structure and describe the geometry of the hydrazine molecule, \(\mathrm{N}_{2} \mathrm{H}_{4} .\) Would you expect this molecule to be polar?

Short answer

Answer: The Lewis structure of the hydrazine molecule (\(\mathrm{N}_{2} \mathrm{H}_{4}\)) consists of two nitrogen atoms connected by a single bond, with each nitrogen atom attached to two hydrogen atoms via single bonds. The molecular geometry around each nitrogen atom is trigonal pyramidal. The hydrazine molecule is considered non-polar due to the cancelation of dipole moments arising from the plane of symmetry.

Step-by-step solution

Determine the total number of valence electrons

Each nitrogen atom (N) has 5 valence electrons, and each hydrogen atom (H) has 1 valence electron. In the hydrazine molecule, there are two nitrogen atoms and four hydrogen atoms, so the total number of valence electrons is: \( (2 \times 5) + (4 \times 1) = 10 + 4 = 14\)

Draw the Lewis structure

To draw the Lewis structure, we should first connect the nitrogen (N) atoms with a single bond and attach two hydrogen (H) atoms to each nitrogen atom with single bonds. Then, we should distribute the remaining valence electrons to complete the octet rule for the nitrogen atoms. The final Lewis structure is: H | H - N - N - H | H

Describe the molecular geometry

According to the Lewis structure, each nitrogen (N) atom is connected to two hydrogen (H) atoms and one other nitrogen atom, while also having one lone pair of electrons. This arrangement can be described as trigonal pyramidal. The geometry around the nitrogen (N) atom is not linear but slightly bent because of the lone pair's presence.

Determine if the molecule is polar or non-polar

A molecule can be considered polar if there is a net dipole moment due to the presence of polar bonds and an asymmetrical arrangement of atoms. While the nitrogen (N) and hydrogen (H) bonds in the hydrazine molecule have some polarity, the molecular structure has a plane of symmetry due to the presence of two identical trigonal pyramidal arrangements around each nitrogen atom. This results in the cancelation of the dipole moments and leads to the hydrazine molecule being considered non-polar. In conclusion, the hydrazine molecule, \(\mathrm{N}_{2} \mathrm{H}_{4}\), has a Lewis structure with two nitrogen atoms connected by a single bond, and each nitrogen atom is attached to two hydrogen atoms with single bonds. The molecular geometry is described as trigonal pyramidal around each nitrogen atom. The molecule is considered non-polar due to the cancelation of dipole moments arising from the plane of symmetry.