Xenon hexafluoride (XeF6) Lewis structure, molecular
geometry or shape, electron geometry, bond angle,
hybridization, formal charges, polar or nonpolar
XeF6 is the molecular formula for xenon hexafluoride, a colorless, odorless, highly reactive gas. It is an inorganic compound that is frequently used as a fluorinating and oxidizing agent in organic synthesis.
XeF6 is also used in the production of uranium hexafluoride (UF6) for nuclear fuel enrichment.
You will find this article very helpful for drawing the Lewis dot structure of XeF6 and for determining its molecular geometry or shape, electron geometry, bond angles, hybridization, formal charges, polarity, etc.
So, without any further delay, let’s find out all you need to know about xenon hexafluoride (XeF6)!
The Lewis structure of xenon hexafluoride (XeF6) comprises a xenon (Xe) atom at the center. It is single-covalently bonded to six fluorine (F) atoms at the sides. The central Xe-atom also consists of a lone pair of electrons, while three lone pairs are present on each terminal F-atom.
Drawing the Lewis structure of XeF6 is quite easy if you follow the simple steps given below.
Steps for drawing the Lewis dot structure of XeF6
1. Count the total valence electrons present in XeF6
XeF6 consists of two distinct elements, i.e., xenon and fluorine.
Xenon (Xe) is a Noble gas element located in Group VIII A (or 18) of the Periodic Table. Thus, it consists of a total of 8 valence electrons in each atom.
Xe is generally unreactive (inert); it reacts to form XeF6 under special experimental conditions only.
In contrast, fluorine (F) is a halogen present in Group VII A (or 17), having a total of 7 valence electrons.
Total number of valence electrons in fluorine = 7
Total number of valence electrons in xenon = 8
The XeF6 molecule comprises 1 Xe-atom and 6 F-atoms.
∴ Therefore, the total valence electrons available for drawing the Lewis dot structure of XeF6= 1(8) + 6(7) = 50 valence electrons.
2. Find the least electronegative atom and place it at the center
By convention, the least electronegative atom out of all those available is chosen as the central atom while drawing the Lewis structure of a molecule.
The least electronegative atom can easily form covalent bonds with other atoms by sharing its electrons.
In XeF6, the two types of elements present are Xe and F.
Fluorine (E.N = 3.98) is the most electronegative element in the Periodic Table; therefore, it cannot be chosen as the central atom.
Hence the less electronegative Xenon (E.N = 2.6) is chosen as the central atom in the XeF6 Lewis structure, while all six F-atoms occupy peripheral positions, as shown below.
3. Connect the outer atoms with the central atom
In this step, all the outer F-atoms are joined to the central Xe-atom using single straight lines.
A straight line represents a single covalent bond, i.e., a bond pair containing 2 electrons.
In the above structure, there are 6 single bonds, i.e., 6(2) = 12 valence electrons are already consumed out of the 50 initially available.
Now let’s explore where we can place the remaining valence electrons.
4. Complete the octet of the outer atoms
An F-atom needs a total of 8 valence electrons to gain a full octet configuration.
A Xe-F bond represents 2 valence electrons surrounding each F-atom, which denotes a deficiency of 6 valence electrons.
Therefore, 3 lone pairs are placed around each F-atom in the XeF6 Lewis structure.
5. Complete the octet of the central atom
Total valence electrons used till step 4 = 6 single bonds + 6 (electrons placed around each F-atom, shown as dots) = 6(2) + 6(6) = 48 valence electrons.
Total valence electrons – electrons used till step 4 = 50 – 48 = 2 valence electrons.
Thus, these 2 valence electrons are placed as a lone pair on the central Xe-atom, which automatically completes its octet.
As a final step, we just need to check the stability of the XeF6 Lewis structure obtained above. Let’s do that by applying the formal charge concept.
6. Check the stability of Lewis’s structure using the formal charge concept
The less the formal charge on the atoms of a molecule, the better the stability of its Lewis structure.
The formal charges can be calculated using the formula given below.
Formal charge = [valence electrons- nonbonding electrons- ½ (bonding electrons)].
Now let us use this formula and the Lewis structure obtained in step 5 to determine the formal charges present on the XeF6 bonded atoms.
What are the electron and molecular geometry of XeF6?
The molecular geometry or shape of XeF6 w.r.t the central Xe-atom is square bipyramidal, also known as distorted octahedral. However, its ideal electronic geometry is pentagonal bipyramidal. The presence of a lone pair of electrons on the central Xe-atom distorts the overall shape and geometry of XeF6.
Molecular geometry of XeF6
The molecular geometry or shape of xenon hexafluoride (XeF6) is square bipyramidal, aka, distorted octahedral.
A lone pair of electrons on the central Xe-atom leads to strong lone pair-bond pair electronic repulsions. This strong repulsive effect distorts the geometry of the molecule. The bonded atoms occupy positions such as to minimize the electron-repulsive effect, thus forming a distorted octahedron.
This molecular shape is also called square bipyramidal, as the 4 F-atoms form a square base while the other 2 F-atoms form pyramids above and below the molecule, as shown below.
Electron geometry of XeF6
According to the valence shell electron pair repulsion (VSEPR) theory of chemical bonding, the ideal electron geometry of a molecule containing a total of 7 electron density regions around the central atom is pentagonal bipyramidal.
In XeF6, the Xe-atom at the center is surrounded by 6 bond pairs, i.e., six Xe-F bonds, and it has a lone pair of electrons, making a total of 7 electron density regions. Hence, the ideal electron pair geometry of the XeF6 molecule is pentagonal bipyramidal.
An easy trick to finding a molecule’s electron and molecular geometry is using the AXN method.
AXN is a simple formula representing the number of bonded atoms and lone pairs on the central atom.
It is used to predict the shape and geometry of a molecule using the VSEPR concept.
AXN notation for XeF6 molecule
A in the AXN formula represents the central atom. In the XeF6 molecule, a xenon (Xe) atom is present at the center, so A = Xe.
X denotes the atoms bonded to the central atom. In XeF6, 6 F-atoms are directly bonded to the central Xe-atom. So, X = 6 for XeF6.
N stands for the lone pairs present on the central atom. As per the Lewis structure of XeF6, the central Xe-atom has 1 lone pair of electrons. Thus, N = 1 for XeF6.
As a result, the AXN generic formula for XeF6 is AX6N1.
Now, you may have a look at the VSEPR chart below.
The VSEPR chart confirms that the molecular geometry or shape of a molecule having AX6N1 generic formula is distorted octahedral. In contrast, its ideal electron geometry is pentagonal bipyramidal, as we already noted down for the XeF6 molecule.
Hybridization of XeF6
The central Xe-atom is sp3d3 hybridized in XeF6.
The electronic configuration of xenon (Xe) is [Kr]4d10 5s2 5p6.
During chemical bonding, the electrons present in 5p atomic orbitals of xenon get unpaired and shift to three empty 5d orbitals.
The one 5s, three 5p and three 5d atomic orbitals of xenon then hybridize to yield seven sp3d3 hybrid orbitals.
One of these seven sp3d3 hybrid orbitals contains paired electrons which are situated as a lone pair on the central Xe-atom in XeF6.
Contrarily, the remaining six half-filled sp3d3 hybrid orbitals form the Xe-F sigma (σ) bonds by overlapping with the half-filled p-orbitals of the fluorine atoms.
Refer to the figure drawn below.
A shortcut to finding the hybridization present in a molecule is using its steric number against the table shown below.
The steric number of the central Xe-atom in XeF6 is 7, so it has sp3d3 hybridization.
Steric number
Hybridization
2
sp
3
sp2
4
sp3
5
sp3d
6
sp3d2
7
sp3d3
The bond angles of XeF6
The atoms forming a square base possess F-Xe-F bond angles exactly equal to 90°. However, the peripheral F-Xe-F bond angles are reduced to 72° due to the distortion present in the molecule.
Is XeF6 polar or nonpolar?
As per Pauling’s electronegativity scale, a polar covalent bond is formed between two dissimilar atoms with an electronegativity difference between 0.4 and 1.6 units.
In XeF6, each Xe-F bond is strongly polar, with a high electronegativity difference of 1.38 units present between a xenon (E.N = 2.6) and a fluorine (E.N = 3.98) atom.
The extremely electronegative F-atoms attract the shared electron cloud away from the central Xe-atom in each Xe-F bond.
The central Xe-atom thus gains a partial positive charge (δ+), while the terminal F-atoms gain partial negative charges (δ–).
It is due to the asymmetrical distorted octahedral shape of XeF6 that the Xe-F dipole moments stay uncancelled to yield an overall polar molecule (net µ > 0).
How can you determine and draw the Lewis structure of XeF6?
The Lewis dot structure of XeF6 displays a total of 50 valence electrons i.e., 50/2 = 25 electron pairs.
An Xe-atom is present at the center of the molecule. It is surrounded by 6 F-atoms by single covalent bonds.
Each F-atom carries 3 lone pairs of electrons while 1 lone pair of electrons is present on the central Xe-atom.
How many bond pairs and lone pairs of electrons are present in the XeF6 Lewis structure?
There are 6 bond pairs and 19 lone pairs of electrons in the Lewis dot structure of XeF6. 1 lone pair is present on the central Xe-atom, while all 6 F-atoms carry 3 lone pairs each.
What is the molecular shape of XeF6?
The molecular geometry or shape of XeF6 is distorted octahedral, also known as square bipyramidal.
Is the molecular geometry of XeF6 the same as its ideal electron pair geometry?
No. The molecular geometry of XeF6 is distorted octahedral, while its ideal electronic geometry is pentagonal bipyramidal.
In the pentagonal bipyramidal electron geometry, 5 electron pairs form the base of a molecule, while 2 electron pairs lie above and below the pentagon, forming a bipyramid.
However, the presence of a lone pair of electrons on the central Xe-atom leads to lone pair-bond pair repulsions, thus distorting the molecular shape of XeF6.
Why are the shapes of XeF6 and IF7 different even though they have the same hybridization and size according to VSEPR?
Iodine pentafluoride (IF7) has an extra bond pair present in it. 7 fluorine atoms surround the central I-atom in IF7, and it has no lone pair of electrons; thus, no lone pair-lone pair and lone pair-bond pair electronic repulsions exist in the molecule.
Hence, IF7occupies a pentagonal bipyramidal shape while that of XeF6is distorted octahedral.
Is the shape of XeF6 and IF6– the same?
Yes. Both XeF6 and IF6– possess a distorted octahedral shape. In both cases, 6 fluorine atoms are covalently bonded to the central atom, which has a lone pair of electrons as well.
The total number of valence electrons available for drawing the xenon hexafluoride (XeF6) Lewis structure is 50.
The molecular geometry or shape of XeF6 is distorted octahedral or square bipyramidal.
The ideal electron pair geometry of XeF6 is pentagonal bipyramidal.
The central Xe-atom is sp3d3 hybridized in XeF6.
The F-Xe-F bond angles in XeF6 are 90° and 72°.
XeF6 is a polar molecule containing strongly polar Xe-F bonds with a high electronegativity difference of 1.38 units between bonded atoms.
Zero or no formal charges on all the bonded atoms in the XeF6 molecule marks the correctness and stability of the Lewis structure obtained in this article.
Vishal Goyal is the founder of Topblogtenz, a comprehensive resource for students seeking guidance and support in their chemistry studies. He holds a degree in B.Tech (Chemical Engineering) and has four years of experience as a chemistry tutor. The team at Topblogtenz includes experts like experienced researchers, professors, and educators, with the goal of making complex subjects like chemistry accessible and understandable for all. A passion for sharing knowledge and a love for chemistry and science drives the team behind the website. Let's connect through LinkedIn: https://www.linkedin.com/in/vishal-goyal-2926a122b/
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