Question

Xenon trioxide is a slightly stable molecule that contains a noble gas. Write the electron dot formula and draw the structural formula for \(\mathrm{XeO}_{3}\).

Short answer

XeO3 has 26 valence electrons. Xenon is double-bonded to each oxygen, with a lone pair on xenon.

Step-by-step solution

Determine the Total Valence Electrons

Xenon \( \text{(Xe)} \) is in group 18 and has 8 valence electrons. Each oxygen (O) is in group 16 and has 6 valence electrons. For \( \mathrm{XeO}_{3} \), the total valence electrons are calculated as follows: \((1 \times 8) + (3 \times 6) = 8 + 18 = 26 \text{ valence electrons}\).

Set Up the Skeletal Structure

In \( \mathrm{XeO}_{3} \), xenon is the central atom. Arrange the three oxygen atoms around the central xenon atom.

Distribute the Electrons as Bonds and Lone Pairs

Place single bonds between the xenon and each oxygen atom. This initially uses up \( 3 \times 2 = 6 \text{ electrons}\). The remaining 20 electrons are to be placed as lone pairs.

Complete the Octet for Terminal Atoms

Add lone pairs to each oxygen atom until they have a complete octet. Each oxygen initially has a single bond (2 electrons); with lone pairs, each oxygen should have 8 electrons total. With three oxygens, this would be \(3 \times 6 = 18\text{ electrons}\).

Place Remaining Electrons on the Central Atom

After distributing 18 electrons to complete the octets of the oxygens, place the remaining 2 electrons as a lone pair on xenon.

Finalize the Structural Formula

Check the structure: Xenon has 5 pairs of electrons (a lone pair and three double bonds), which completes its expanded octet capacity. The structure should show xenon in the center, each oxygen double-bonded to xenon.

Key concepts

Lewis Structures

Lewis structures are a foundational concept in understanding chemical bonding. These structures help represent the arrangement of electrons in a molecule, showing how atoms are bonded and where lone pairs of electrons exist. For xenon trioxide (\( \text{XeO}_3 \)), we first determine the total number of valence electrons, which governs how these electrons are distributed.

• Calculate the total valence electrons available: In \( \text{XeO}_3 \), xenon contributes 8 electrons, and the three oxygen atoms contribute a total of 18 electrons, giving us 26 valence electrons overall.
• Arrange the skeletal structure: Typically, the less electronegative atom, xenon in this case, is placed in the center, with oxygen atoms surrounding it.
• Connect the atoms first with single bonds and then distribute the remaining electrons to ensure each atom satisfies its octet rule, a guideline stating that atoms tend to form bonds until they have eight electrons in their valence shell.

Using this systematic approach, we construct a visual representation of the molecule's structure, which can then be used to infer further chemical properties.

Valence Electrons

Valence electrons are the electrons located in the outer shell of an atom and play a crucial role in chemical bonding. They are primarily involved in forming bonds, such as ionic or covalent bonds. Understanding how electrons are shared or transferred helps us predict the structure and reactivity of molecules.

• Xenon is a noble gas with 8 valence electrons, which means it can expand its octet, a unique feature of elements beyond the second period.
• Each oxygen contributes 6 valence electrons and typically seeks to complete its octet by sharing or accepting electrons through bonds.
• In \( \text{XeO}_3 \), each oxygen atom forms double bonds with the central xenon atom, using up a shared pair of electrons from xenon's valence shell.

Knowing the configuration and tendency of these valence electrons allows us to predict and draw the Lewis structure of the molecule, revealing its potential interactions and stability.

Molecular Geometry

Molecular geometry refers to the 3D layout of atoms within a molecule, dictating its shape and influencing physical and chemical properties. For \( \text{XeO}_3 \), understanding its geometry helps us predict how it interacts with other substances.Features of molecular geometry for \( \text{XeO}_3 \):

• The central xenon atom has five pairs of electrons, including three bonding pairs with oxygen atoms and one lone pair, influencing the bond angles and overall shape.
• The molecular shape of \( \text{XeO}_3 \) is described as trigonal pyramidal, due to the lone pair pushing the bonded pairs slightly downward, away from the lone pair.
• This geometry affects the molecule's polarity, reactivity, and interaction with other molecules or surfaces.

Understanding molecular geometry provides insights into the behavior of the molecule in various chemical contexts, essentially guiding us in predicting properties like boiling point, solubility, and reactivity.