Which of the following does not have tetrahedral structure ?

Question

Accepted Answer

Option 4, $XeF_4$, is the correct answer because it does not have a tetrahedral structure. Instead, $XeF_4$ has a square planar structure. This can be explained by considering the electron geometry and molecular geometry of $XeF_4$:

1. **Electron Geometry and Hybridization**: Xenon (Xe) in $XeF_4$ is the central atom and has eight valence electrons. When it forms bonds with four fluorine atoms, it uses four of these electrons to form four sigma bonds with fluorine. The remaining four electrons form two lone pairs. The hybridization of xenon in $XeF_4$ is $sp^3d^2$, which corresponds to an octahedral electron geometry.

2. **Molecular Geometry**: Due to the presence of two lone pairs, the molecular geometry is not octahedral but rather square planar. The lone pairs occupy positions opposite each other, minimizing repulsion, and the four fluorine atoms form a square plane around the xenon atom.

Now, let's explain why each of the other options is incorrect:

1. **$PO_4^{3-}$**: The phosphate ion has a tetrahedral structure. Phosphorus is the central atom, and it forms four sigma bonds with oxygen atoms. The hybridization of phosphorus is $sp^3$, which results in a tetrahedral geometry.

2. **$SO_4^{2-}$**: The sulfate ion also has a tetrahedral structure. Sulfur is the central atom, forming four sigma bonds with oxygen atoms. The hybridization of sulfur is $sp^3$, leading to a tetrahedral geometry.

3. **$BF_4^-$**: The tetrafluoroborate ion has a tetrahedral structure. Boron is the central atom, forming four sigma bonds with fluorine atoms. The hybridization of boron is $sp^3$, resulting in a tetrahedral geometry.

In summary, $XeF_4$ is the only molecule among the options that does not have a tetrahedral structure. It has a square planar structure due to the presence of two lone pairs on the central xenon atom, which distinguishes it from the other options that all have tetrahedral geometries.