Question

Which of the following statements is/are true? Correct the false statements. a. It is impossible to satisfy the octet rule for all atoms in \(\mathrm{XeF}_{2}\) b. Because \(\mathrm{SF}_{4}\) exists, OF, should also exist, because oxygen is in the same family as sulfur. c. The bond in \(\mathrm{NO}^{+}\) should be stronger than the bond in \(\mathrm{NO}^{-}\) d. As predicted from the two Lewis structures for ozone, one oxygen-oxygen bond is stronger than the other oxygen-oxygen bond.

Short answer

The short answer: a. False - It is possible to satisfy the octet rule for F atom, and Xe can have more than 8 valence electrons in XeF2. b. False - Although SF₄ exists, OF₄ does not exist, because oxygen's smaller size and higher electronegativity prevent it from forming four bonds with fluorine. c. True - In NO⁺, the molecule is left with a double bond between the nitrogen and oxygen atoms, which leads to stronger bond strength. In the case of NO⁻, the molecule has a single bond and lone electron pairs, resulting in a lower bond strength. d. False - Although there are two different Lewis structures for ozone, both oxygen-oxygen bonds are equal in strength due to resonance.

Step-by-step solution

Statement a Analysis

It is claimed that it is impossible to satisfy the octet rule for all atoms in XeF2. Let's first recall the octet rule: atoms tend to gain, lose, or share electrons to reach a stable electron configuration with 8 electrons in their valence shell. Now, let's try to create the Lewis structure of XeF2. Xe has 8 valence electrons since it belongs to Group 18, and F has 7 valence electrons since it belongs to Group 17. Two F atoms can make single bonds with Xe, resulting in Xe having a total of 10 valence electrons. However, since Xe is from Group 18 and can have more than 8 valence electrons, the octet rule doesn't apply to Xe.

.Statement a Answer

The statement is false because it is possible to satisfy the octet rule for all atoms in XeF2. The corrected statement would be: It is possible to satisfy the octet rule for F atom, and Xe can have more than 8 valence electrons in XeF2.

Statement b Analysis

The statement claims that because SF₄ exists, OF₄ should also exist. Both sulfur and oxygen are part of Group 16 in the periodic table, so they share several chemical properties. However, we must consider their atomic radii and electronegativity. Oxygen, being smaller and more electronegative compared to sulfur, will have a difficult time forming four bonds with fluorine.

Statement b Answer

The statement is false because having the same group in the periodic table does not always imply that similar compounds can exist. The corrected statement would be: Although SF₄ exists, OF₄ does not exist, because oxygen's smaller size and higher electronegativity prevent it from forming four bonds with fluorine.

Statement c Analysis

The statement suggests that the bond in NO⁺ should be stronger than the bond in NO⁻. In order to determine the bond strength, we must analyze resonance structures and differences in electron densities in both molecules.

Statement c Answer

The statement is true. In NO⁺, the molecule is left with a double bond between the nitrogen and oxygen atoms, which leads to stronger bond strength. In the case of NO⁻, the molecule has a single bond and lone electron pairs, resulting in a lower bond strength.

Statement d Analysis

The statement claims that in ozone, one oxygen-oxygen bond is stronger than the other oxygen-oxygen bond based on the Lewis structures. We must consider the resonance in ozone's Lewis structures to determine if this is true.

Statement d Answer

The statement is false because in ozone, due to resonance, both oxygen-oxygen bonds are equal, and the bond strength is intermediate between a single bond and a double bond. The corrected statement would be: Although there are two different Lewis structures for ozone, both oxygen-oxygen bonds are equal in strength due to resonance.

Key concepts

Octet Rule

The octet rule is a fundamental chemical principle which posits that atoms are most stable when they have eight electrons in their valence shell. This configuration is reminiscent of the electron arrangement found in noble gases, which are known for their chemical inertness.

For example, when we consider the molecule \textbf{Xenon difluoride} (\textbf{XeF}\(_2\)), the rule suggests that each fluorine (F) atom seeks to complete its octet by sharing electrons. Xenon (Xe), being a noble gas, normally has a complete octet, but it can hold more than eight electrons due to its capacity to use empty d-orbitals. Here, Xenon breaks the octet rule by having more than eight electrons—something that's possible for elements in period 3 and beyond due to their larger size and ability to expand their valence shell.

The octet rule serves as a helpful guideline in drawing Lewis structures for molecules. However, it's crucial to remember that there are exceptions: molecules and ions like \textbf{XeF}\(_2\) do not always follow the octet rule, particularly when dealing with elements beyond the second period of the periodic table.

Resonance Structures

Resonance structures are a way of representing molecules where the atomic framework remains constant, but the distribution of electrons can vary across several legitimate Lewis structures. These multiple structures, known as resonance forms, describe delocalization of electrons within the molecule.

Take ozone (\textbf{O}\(_3\)) as an example. It has two resonance forms that differ in the location of the double bond. Neither form truly represents the actual bonding within the molecule; instead, they provide an 'average' depiction of where the electrons can be. Because of this electron delocalization, the two bonds in ozone are indeed equivalent, and the molecule exhibits bond lengths and strengths that are between those of a single and a double bond.

Resonance is not a flickering between structures but rather a simultaneous representation of all possible structures. It's important to correctly depict possible resonance forms and understand that the actual bond characteristics in the molecule are a hybridization of those forms.

Bond Strength

Bond strength refers to how strongly two atoms are held together in a molecule, and it is directly related to the energy required to break the bond. Stronger bonds have higher bond energies. Factors such as bond length, bond order, and the presence of charges influence bond strength.

Considering the molecule \textbf{Nitrogen monoxide} (\textbf{NO}\(^+\)) and its counterpart (\textbf{NO}\(^-\)), we find a clear example of how charges affect bond strength. In \textbf{NO}\(^+\), there is a double bond (a bond order of 2) between the nitrogen and oxygen, which makes the bond stronger due to the greater sharing of electrons. Conversely, in \textbf{NO}\(^-\), the presence of an extra electron results in a weaker single bond (a bond order of 1) as the additional electron repulsion reduces the bond strength.

This is an essential concept in chemistry because it helps explain the reactivity and stability of different molecules. Bonds are not static; they are dynamic and can be affected by their molecular environment. Understanding bond strength is crucial when predicting the behavior of molecules under various conditions.