Chapter 7: Problem 47
Which of these molecules has a net dipole moment? For each of the polar molecules, indicate the direction of the dipole in the molecule. (a) nitrosyl fluoride, FNO (b) disulfur difluoride, \(\mathrm{S}_{2} \mathrm{~F}_{2}\)
Short Answer
Expert verified
Both FNO and \( \mathrm{S}_{2} \mathrm{F}_{2} \) are polar with net dipole moments.
Step by step solution
01
Determining the Molecular Geometry
Examine the molecules to determine their geometry. Using VSEPR theory, for FNO, the geometry is bent due to the presence of lone pairs on the nitrogen atom. For \( \mathrm{S}_{2} \mathrm{F}_{2} \), it has a distorted structure often related to a V-shape due to variations in electron repulsion.
02
Electronegativity Differences
Identify the electronegative atoms in each molecule. In FNO, fluorine (F) is more electronegative than both nitrogen (N) and oxygen (O). In \( \mathrm{S}_{2} \mathrm{F}_{2} \), fluorine (F) is more electronegative than sulfur (S). This causes an uneven distribution of charges in the molecules.
03
Calculating the Net Dipole Moment
Determine if the polar bonds result in a net dipole moment. In FNO, the polar bonds between N-F and N-O do not cancel each other out because of the bent shape, leading to a net dipole moment directed towards the fluorine. For \( \mathrm{S}_{2} \mathrm{F}_{2} \), the dipole moments primarily from the S-F bonds may or may not cancel out depending on the precise molecular shape. Generally, due to its unique geometry, it does have a net dipole moment.
04
Indicating Dipole Directions
Indicate the direction of the dipole moment for the polar molecules. For nitrosyl fluoride, the dipole moment points from nitrogen towards fluorine due to fluorine's higher electronegativity. In \( \mathrm{S}_{2} \mathrm{F}_{2} \), if there is a net dipole moment, it is directed away from the S-S bond towards the more electronegative fluorine atoms.
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Key Concepts
These are the key concepts you need to understand to accurately answer the question.
Molecular Geometry
Molecular geometry is the three-dimensional arrangement of atoms within a molecule. This configuration affects a molecule's physical and chemical properties.
Understanding the molecular geometry helps predict how molecules interact with each other and their behavior in different chemical reactions. In this context, the shape of the molecule is crucial in determining its dipole moment.
Some common molecular shapes include linear, bent, tetrahedral, trigonal planar, and trigonal bipyramidal. The geometry of a molecule is influenced by the number of electron regions (bonding or non-bonding electron pairs) around a central atom. For example, the bent shape in nitrosyl fluoride (FNO) results from lone pairs repelling bonding pairs, causing the molecule to not be linear.
Understanding the molecular geometry helps predict how molecules interact with each other and their behavior in different chemical reactions. In this context, the shape of the molecule is crucial in determining its dipole moment.
Some common molecular shapes include linear, bent, tetrahedral, trigonal planar, and trigonal bipyramidal. The geometry of a molecule is influenced by the number of electron regions (bonding or non-bonding electron pairs) around a central atom. For example, the bent shape in nitrosyl fluoride (FNO) results from lone pairs repelling bonding pairs, causing the molecule to not be linear.
Electronegativity
Electronegativity is the ability of an atom to attract electrons towards itself in a bond. It plays a significant role in bond formation and determines how electrons are distributed among bonded atoms.
Atoms with higher electronegativity values tend to attract electrons more effectively, creating an uneven charge distribution. This can create partial charges on different parts of a molecule, leading to polar bonds.
In the exercise, fluorine is the most electronegative element present in both FNO and \( S_2F_2 \). This causes the electrons to be pulled closer to the fluorine atoms, resulting in polar bonds. The disparity in electronegativity between bonded atoms contributes to the overall molecular polarity and can influence whether a molecule has a net dipole moment.
Atoms with higher electronegativity values tend to attract electrons more effectively, creating an uneven charge distribution. This can create partial charges on different parts of a molecule, leading to polar bonds.
In the exercise, fluorine is the most electronegative element present in both FNO and \( S_2F_2 \). This causes the electrons to be pulled closer to the fluorine atoms, resulting in polar bonds. The disparity in electronegativity between bonded atoms contributes to the overall molecular polarity and can influence whether a molecule has a net dipole moment.
VSEPR Theory
Valence Shell Electron Pair Repulsion (VSEPR) theory is a model used to predict the molecular geometry based on the idea that repulsion between electron pairs causes them to arrange themselves as far apart as possible.
VSEPR considers both bonding and non-bonding electron pairs around a central atom. Non-bonding pairs, often called lone pairs, exert a greater repulsive force than bonding pairs, potentially altering the shape of molecules.
For example, in FNO, the presence of lone electron pairs on nitrogen shapes the molecule into a bent form, preventing a linear structure. In \( S_2F_2 \), the electron repulsions from lone pairs and bonding pairs lead to a V-shape, which does not allow the dipoles to cancel out in most of its configurations. This results in a net dipole moment.
VSEPR considers both bonding and non-bonding electron pairs around a central atom. Non-bonding pairs, often called lone pairs, exert a greater repulsive force than bonding pairs, potentially altering the shape of molecules.
For example, in FNO, the presence of lone electron pairs on nitrogen shapes the molecule into a bent form, preventing a linear structure. In \( S_2F_2 \), the electron repulsions from lone pairs and bonding pairs lead to a V-shape, which does not allow the dipoles to cancel out in most of its configurations. This results in a net dipole moment.
Polar Molecules
Polar molecules have an uneven distribution of electron density. This means one end of the molecule has a slight positive charge while the other has a slight negative charge, indicated by a dipole moment.
The presence of polar bonds doesn't always guarantee that the entire molecule is polar. It's the molecular geometry that determines if the dipoles cancel out or lead to a net dipole moment.
For instance, nitrosyl fluoride is polar due to its bent shape, causing the dipole moments dictated by the N-F and N-O bonds not to cancel. Similarly, \( S_2F_2 \) is polar because its non-linear structure leads to an asymmetrical distribution of polar bonds' dipoles, which don't negate each other effectively. Thus, understanding both the bond polarities and the molecular shapes is essential to determine the polarity of molecules.
The presence of polar bonds doesn't always guarantee that the entire molecule is polar. It's the molecular geometry that determines if the dipoles cancel out or lead to a net dipole moment.
For instance, nitrosyl fluoride is polar due to its bent shape, causing the dipole moments dictated by the N-F and N-O bonds not to cancel. Similarly, \( S_2F_2 \) is polar because its non-linear structure leads to an asymmetrical distribution of polar bonds' dipoles, which don't negate each other effectively. Thus, understanding both the bond polarities and the molecular shapes is essential to determine the polarity of molecules.