Question

Predict the electron pair geometry for the xenon atom in \(\mathrm{XeOF}_{4}\) (a) linear (b) trigonal bipyramid (c) trigonal planar (d) octahedral (e) tetrahedral

Short answer

(d) octahedral

Step-by-step solution

Identify Valence Electrons

Xenon (Xe) has 8 valence electrons, while oxygen (O) contributes 2 electrons to the bond, and each fluorine (F) contributes 1 electron. In total, the molecule \( \text{XeOF}_4 \) has \( 8 + 2 + 4 \times 1 = 14 \) valence electrons.

Determine the Steric Number

The steric number is the sum of the bonded atoms around xenon and lone pairs on xenon. \( \text{XeOF}_4 \) has 5 bonded atoms (1 oxygen and 4 fluorines) and 1 lone pair on xenon, giving a steric number of 6.

Identify Electron Pair Geometry

With a steric number of 6, the electron pair geometry or electron domain geometry is octahedral. This includes both bonded atoms and lone pairs.

Confirm Answer with Options

Among the given choices, (d) octahedral matches the calculated electron pair geometry for \( \text{XeOF}_4 \).

Key concepts

Valence Electrons

Valence electrons are the outermost electrons of an atom and play a crucial role in chemical bonding and molecular geometry. Essentially, these are the electrons that participate in the formation of chemical bonds with other atoms. To determine the electron pair geometry of a molecule like \( \text{XeOF}_4 \), it’s important to first identify the number of valence electrons.

• Xenon (Xe) has 8 valence electrons because it is in group 18 of the periodic table.
• Oxygen (O) contributes 2 electrons to the chemical bond because it typically forms two bonds.
• Each fluorine (F) contributes 1 electron to its bond, and there are four fluorine atoms in \( \text{XeOF}_4 \).

Adding these together, the molecule \( \text{XeOF}_4 \) has a total of 14 valence electrons. This initial electron count is the first step in predicting the shape and geometry of the molecule. Understanding valence electrons help students appreciate how atoms come together to form compounds and determine their configurations.

Steric Number

The steric number is a key parameter in identifying molecular geometry. It is the total number of bonds and lone pairs of electrons around a central atom. In the context of \( \text{XeOF}_4 \), this is calculated by adding:

• 5 bonded atoms (1 oxygen and 4 fluorine atoms)
• 1 lone pair of electrons on the xenon atom

Giving a steric number of 6 for xenon in \( \text{XeOF}_4 \). This value is significant because it determines the electron-pair geometry of the compound. A higher steric number indicates more bonds and/or lone pairs around the central atom, often resulting in more complex geometries. By understanding the steric number, students can better predict how molecules will form specific shapes.

Octahedral Geometry

Octahedral geometry is a specific electron pair geometry characterized by a central atom surrounded by six regions of electron density. It is named after its resemblance to the shape of an octahedron, which has eight faces. When considering steric numbers, a value of 6 usually leads to an octahedral arrangement.In the case of \( \text{XeOF}_4 \), the steric number is 6 (five bonded atoms and one lone pair), which indicates an octahedral electron pair geometry. This arrangement allows for the molecule to minimize electron repulsion, distributing the electron pairs evenly in three-dimensional space.However, it is essential to note that the presence of lone pairs alters the molecular shape slightly from a perfect octahedron. Instead, chemical bonds can be slightly bent to accommodate electron repulsion from the lone pair. By learning about octahedral geometry, students can conclude the possible molecular shapes and predict chemical behaviors effectively.