Question

Two different compounds exist having the formula \(\mathrm{N}_{2} \mathrm{F}_{2}\) . One compound is polar whereas the other is nonpolar. Draw Lewis structures for \(\mathrm{N}_{2} \mathrm{F}_{2}\) consistent with these observations.

Short answer

The two different Lewis structures for \(\mathrm{N}_{2}\mathrm{F}_{2}\) are: 1. Polar compound with a bent geometry: ``` F F \ / N - N / \ F F ``` 2. Nonpolar compound with a linear geometry: ``` F F \ / N = N / \ F F ``` The polar structure has an unequal distribution of electron density, resulting in a net molecular dipole moment, while the nonpolar structure has a symmetrical electron distribution with no net molecular dipole moment.

Step-by-step solution

Understand the Concept of Polarity

Polarity occurs in a molecule when there is an unequal distribution of electron density, resulting in a molecular dipole moment, caused by atoms with different electronegativities bonded together or a non-symmetrical arrangement of atoms. A polar molecule will have a partial positive charge on one side and a partial negative charge on the other side. On the other hand, a nonpolar molecule has no net molecular dipole moment, and its electron distribution is symmetrical.

Draw Lewis Structure for Polar \(\mathrm{N}_{2}\mathrm{F}_{2}\) Compound

To draw a Lewis structure for the polar \(\mathrm{N}_{2}\mathrm{F}_{2}\) compound, we need to create a structure where there is an unequal distribution of electron density. The most likely structure that satisfies this condition is a bent geometry. Here's how to draw the polar Lewis structure: 1. Place an N atom at the central position and connect it with the other N atom. 2. Attach one F atom to each N atom. 3. Complete octets for all atoms by adding lone pairs of electrons. N atoms will have one lone pair and F atoms will have three lone pairs each. The resulting structure is: ``` F F \ / N - N / \ F F ``` In this structure, the electron density is not distributed symmetrically, and there is a net molecular dipole moment, making it a polar molecule.

Draw Lewis Structure for Nonpolar \(\mathrm{N}_{2}\mathrm{F}_{2}\) Compound

To draw a Lewis structure for the nonpolar \(\mathrm{N}_{2}\mathrm{F}_{2}\) compound, we need an arrangement of atoms that leads to a symmetrical electron distribution and no net molecular dipole moment. Here's how to draw the nonpolar Lewis structure: 1. Place an N atom at the central position and connect it with the other N atom via a double bond. 2. Attach one F atom to each N atom. 3. Complete octets for all atoms by adding lone pairs of electrons. N atoms will have one lone pair and F atoms will have three lone pairs each. The resulting structure is: ``` F F \ / N = N / \ F F ``` In this structure, the electron density is distributed symmetrically, and there is no net molecular dipole moment, making it a nonpolar molecule. In summary, we have drawn two different Lewis structures for \(\mathrm{N}_{2}\mathrm{F}_{2}\): one with a bent geometry being polar and the other with a linear geometry being nonpolar.

Key concepts

Molecular Polarity

Molecular polarity is a fundamental concept in chemistry that helps us understand why some molecules behave the way they do. It involves the unequal distribution of electrons in a molecule. Polarity occurs when electronegativity differences between bonded atoms create partial charges.
This results in a dipole moment where one part of the molecule becomes partially positive and the other part becomes partially negative. For example, in the polar version of the \(\mathrm{N}_2\mathrm{F}_2\) molecule, the molecular shape doesn’t allow the charges to cancel out, leading to an overall dipole moment.
Conversely, nonpolar molecules have a symmetrical arrangement of atoms. This symmetry effectively balances out the electron distribution, making the molecule have an even charge distribution with no net dipole moment. Think of it like a perfectly balanced seesaw, where the weight is equally distributed on both sides.

Octet Rule

The octet rule is a guiding principle in drawing Lewis structures. It states that atoms are generally more stable when they have eight electrons in their valence shell, resembling a noble gas configuration.
For most main group elements, achieving this configuration is akin to reaching an energy-efficient state. In the case of nitrogen in the \(\mathrm{N}_2\mathrm{F}_2\) molecule, each nitrogen atom is bonded both to another nitrogen atom and to a fluorine atom. By sharing electrons through these bonds, they can both satisfy the octet rule.
Fluorine, being highly electronegative, also adheres strictly to the octet rule by sharing one of its electrons with nitrogen, completing its own outer shell as well. This results in a stable and energetically favorable distribution of electrons.

Molecular Geometry

Molecular geometry is all about the three-dimensional arrangement of atoms in a molecule. It greatly influences the physical and chemical properties of a compound. In the example of \(\mathrm{N}_2\mathrm{F}_2\), the molecular geometry is what differentiates the polar from the nonpolar molecule.
In the polar variation of \(\mathrm{N}_2\mathrm{F}_2\), the geometry can be described as bent due to the arrangement of the atoms and the lone pairs on the nitrogen atoms. This shape causes a lack of symmetry, resulting in a net dipole moment.
In the nonpolar variant, the geometry is more linear because the electron clouds are distributed symmetrically. This symmetry cancels out any potential dipole moments across the molecule, leading to a nonpolar nature. The differing geometries highlight how a simple change in the arrangement of atoms can alter molecular characteristics significantly.

Dipole Moment

Dipole moment is a measure of molecular polarity. It indicates how much separation of charge exists within a molecule and is measured in units called Debye. A dipole moment arises in a molecule if the centers of positive and negative charges do not coincide.
In the context of \(\mathrm{N}_2\mathrm{F}_2\), the polar molecule possesses a significant dipole moment because the bent geometry prevents the cancellation of the dipoles from each bond. The unequal sharing of electrons leads to this measurable dipole moment, indicating a net polarization.
Conversely, the nonpolar structure with its symmetrical geometry doesn’t have a dipole moment. Its electron cloud distribution is even, reflecting the uniformity of charge. Understanding dipole moments is crucial as they influence how molecules interact with external fields and other molecules, affecting properties like solubility and boiling points.