Question

In which of the following compounds, the Fluorine atoms are placed axially in a trigonal bipyramidal geometry?

• A.
• B.
• C.
• D.

Answer 1

Answer: (A), (C), (D)

The correct options are
A
C
D

We had earlier seen that $Xe{F}_2$ has a linear shape. The 3 lone pairs of electrons of central Xe atom lie on the plane perpendicular to the axial Xe – F bonds. The molecule has a trigonal bipyramidal geometry

In this molecule, if one oxygen atom takes the place of a lone pair, we get the geometry of $XeO{F}_2$. Do note that Xenon has a double bond with the oxygen atom. Let us look at the ground state and excited state:

Let us look at the geometry:

Now try to deduce the shape and geometry of $Xe{O}_2{F}_2$:
A logical leap is to assume that the structure would be similar to replacing two of the three lone pairs with two oxygen atoms in the $Xe{F}_2$ structure. It is a good guess!

As for the geometry, $Xe{F}_2$, $XeO{F}_2$ and $Xe{O}_2{F}_2$ all have the same trigonal bipyramidal geometry. $Xe{F}_2$ has a linear shape. $XeO{F}_2$ is T - Shaped. $Xe{O}_2{F}_2$ is see-saw shaped.
Earlier we had seen that the geometry of $Xe{F}_4$ has a square bipyramidal geometry and square planar shape:


In the above geometry, if we replace a lone pair with an Oxygen atom such that there is a double bond between Xe and O, then we get the geometry of $XeO{F}_4$. The four F atoms line in a plane perpendicular to the Xe – O axial sigma bond. This geometry is still the same as $Xe{F}_4$ but the shape will be square pyramidal!

So correct options are a c and d