Shape of XeO₄ is:

• A. Octahedral
• B. Square pyramidal
• C. Pyramidal
• D. T-shaped

The shape of XeO4, or xenon tetroxide, is best described as **square pyramidal**. So, the correct answer is B. Square pyramidal. Let’s delve into why this is the case by examining the molecular geometry and the factors that influence it.

Understanding Molecular Geometry

Molecular geometry refers to the three-dimensional arrangement of atoms in a molecule. It is determined by the number of bonding pairs and lone pairs of electrons around the central atom. In the case of XeO4, xenon (Xe) is the central atom surrounded by four oxygen (O) atoms.

Electron Pair Geometry

To determine the shape of XeO4, we first need to consider its electron pair geometry. Xenon has a total of 8 valence electrons. When it forms XeO4, it uses four of these electrons to form double bonds with four oxygen atoms. This leaves us with 4 bonding pairs and no lone pairs on the xenon atom.

VSEPR Theory Application

According to VSEPR (Valence Shell Electron Pair Repulsion) theory, the arrangement of electron pairs around a central atom will adopt a geometry that minimizes repulsion between them. For XeO4, with four bonding pairs and no lone pairs, the electron pair geometry is based on a tetrahedral arrangement. However, because we have a central atom bonded to four other atoms, we need to consider the actual molecular shape.

Determining the Molecular Shape

In XeO4, the four oxygen atoms are arranged around the xenon atom. The presence of four bonding pairs leads to a square planar arrangement of the oxygen atoms, but since we have a central atom with a tetrahedral electron pair geometry, the actual molecular shape becomes square pyramidal. This is because the geometry accounts for the spatial arrangement of the bonded atoms, where one of the positions is effectively "filled" by the central atom (xenon) while the others are occupied by the oxygen atoms.

Visualizing the Structure

To visualize this, imagine a pyramid with a square base. The xenon atom sits at the apex of the pyramid, while the four oxygen atoms form the corners of the square base. This arrangement minimizes the repulsion between the electron pairs and stabilizes the molecule.

Conclusion

In summary, the molecular shape of XeO4 is square pyramidal due to the arrangement of its four bonding pairs around the xenon atom. This shape is a direct result of the tetrahedral electron pair geometry influenced by the bonding interactions with the oxygen atoms. Understanding these concepts helps clarify why certain molecules adopt specific shapes, which is crucial in predicting their chemical behavior and reactivity.