Question

\mathrm{Xenon}\( forms \)\mathrm{XeO}_{3}, \mathrm{XeO}_{4}\(, and \)\mathrm{XeO}_{6}^{4-}\(, all of which are powerful oxidizing agents. Give their Lewis structures, their bond angles, and the hybridization of the xenon atom. Which would be expected to have the longest \)\mathrm{Xe}-\mathrm{O}$ distances?

Short answer

The Lewis structures for XeO3, XeO4, and XeO6^4- show that Xe is sp3 hybridized in XeO3 and XeO4, and sp3d3 hybridized in XeO6^4-. XeO3 has a trigonal pyramidal geometry with angles <109.5°, XeO4 has a tetrahedral geometry with 109.5° angles, and XeO6^4- has a pentagonal pyramidal geometry with varied angles. The longest Xe-O bond distances are expected in XeO6^4- due to its larger hybrid orbitals and expanded valence shell.

Step-by-step solution

Draw the Lewis Structures

Begin by counting the valence electrons for xenon. Xenon has 8 valence electrons. Oxygen has 6 valence electrons, but in ions and compounds, it usually forms two bonds and has two lone pairs, completing its octet. For each compound, these electrons will be distributed amongst the oxygen atoms and any additional electrons will be placed on the xenon atom.- For XeO3, xenon shares 2 electrons with each of the 3 oxygen atoms, with the single pairs on the oxygen atoms completing their octet. No charges are necessary, and Xe has a total of 6 electrons in its valence shell (each O bonding pair is counted once).- For XeO4, xenon shares 2 electrons with each of the 4 oxygen atoms. Again, oxygen completes its octet with lone pairs, and no charges are needed. Xenon now has 8 electrons around it, satisfying the octet rule.- For XeO6^4-, xenon shares 2 electrons with each of the 6 oxygen atoms. Because of the 4- charge, there are 4 extra electrons, which are placed on the xenon atom as lone pairs. Xe in this ion has 12 electrons in its valence shell, exceeding the octet rule.

Predict the Bond Angles

Using the VSEPR (Valence Shell Electron Pair Repulsion) model, predict the bond angles based on the arrangement of electron pairs around the central xenon atom.- XeO3 has 3 bonding pairs and 1 lone pair on the xenon atom, which corresponds to a trigonal pyramidal shape, with bond angles slightly less than 109.5 degrees due to the repulsion of the lone pair.- XeO4 has 4 bonding pairs and no lone pairs on the xenon atom, which corresponds to a tetrahedral shape with bond angles of 109.5 degrees.- XeO6^4- has 6 bonding pairs and 1 lone pair on the xenon atom, resulting in a distorted octahedral shape known as a pentagonal pyramidal, which results in varied bond angles.

Determine Hybridization

Hybridization depends on the number of electron domains (regions of high electron density) around the central atom.- XeO3 has 4 electron domains (3 bonds + 1 lone pair), leading to sp3 hybridization.- XeO4 has 4 electron domains (4 bonds), also leading to sp3 hybridization.- XeO6^4- has 7 electron domains (6 bonds + 1 lone pair), which corresponds to sp3d3 hybridization.

Longest Xe-O Distance Determination

The longest Xe-O bond distance would typically be associated with the ion/molecule where the central xenon atom has the greatest electron density around it, which results in greater repulsion and longer bond lengths.- XeO3 with sp3 hybridization implies smaller atomic orbitals compared to the larger d orbitals in XeO6^4-.- XeO4, also with sp3 hybridization, might suggest similar bond lengths to XeO3.- XeO6^4-, however, has sp3d3 hybridization involving d orbitals that are generally larger, thus it can be expected to have the longest Xe-O distances given the expansion to accommodate the additional lone pair and the 6 bonding pairs.

Key concepts

Chemical Bonding in Xenon Compounds

Chemical bonding is the force that holds atoms together in molecules. In the case of xenon compounds like XeO3, XeO4, and XeO6^4-, bonding involves the sharing of electrons. Xenon, a noble gas, is known for its complete valence shell, but under certain conditions, it can form covalent bonds with other elements like oxygen.

In the Lewis structures for these compounds, Xe shares electrons with O atoms to form stable molecules. The number of shared electrons depends on the compound, with XeO3 and XeO4 following the octet rule, while XeO6^4- expands the octet due to additional electrons from its 4- charge. This exception to the octet rule is possible because xenon has available d-orbitals that can accommodate more than eight electrons. The presence of lone pairs or additional bonds alters the electron density around the xenon, influencing the bond angles and lengths.

VSEPR Theory Applied to Xenon Compounds

VSEPR theory, which stands for Valence Shell Electron Pair Repulsion, provides insight into the shapes of molecules and the angles between bonds. This theory posits that electron pairs around a central atom will arrange themselves to minimize repulsion.

For XeO3, VSEPR predicts a trigonal pyramidal shape due to three bonding pairs and one lone pair. The lone pair has a greater repulsive force, slightly reducing the bond angles from the ideal tetrahedral angle of 109.5 degrees. XeO4, with four bonding pairs and no lone pairs, has a perfect tetrahedral shape with bond angles of exactly 109.5 degrees. Lastly, XeO6^4- with its six bonding pairs and one lone pair has a distorted octahedral shape, often referred to as pentagonal pyramidal, resulting in varied bond angles. These shapes and angles can affect the physical and chemical properties of the molecules.

Hybridization in Xenon Compounds

Hybridization is a concept in molecular chemistry that describes the mixing of atomic orbitals to form new hybrid orbitals, which can accommodate bonding and lone electron pairs. This concept helps explain the geometry of electron pairs around the central atom in molecules.

For xenon compounds, the type of hybridization corresponds to the number of electron domains around the xenon atom. XeO3 and XeO4 both have sp3 hybridization, comprising one s orbital and three p orbitals, reflecting the tetrahedral electron pair geometry. However, XeO6^4- with its additional electron pairs extends beyond sp3 to sp3d3 hybridization, involving s, p, and d orbitals. The inclusion of d orbitals allows for a higher number of electron domains, fitting with the 'expanded octet' that xenon exhibits in this compound. Often, the type of hybridization can influence bond angles and lengths, as seen with the longer Xe-O bonds in XeO6^4- due to the larger d orbitals involved.