Question

The geometry of $Xe{O}_3$ is ________.
(A) linear
(B) planar
(C) pyramidal
(D) T-shaped

Answer 1

Hint: Start by writing electronic configuration in Xenon oxide. Calculate the number of electron pairs in the given molecule, $Xe{O}_3$. Find out the hybridization of $Xe{O}_3$ and draw the structure accordingly.

Complete step by step answer:
- Xenon belongs to the group of inert gases and it has the atomic number 54.
- Its electronic configuration is,
$$Xe=1s^{2}2s^{2}2p^{6}3s^{2}3p^{6}4s^{2}3d^{10}4p^{6}5s^{2}4d^{10}5p^6$$

- Oxygen has the atomic number 8. Its electronic configuration is,
$$O=1s^{2}2s^{2}2p^4$$
- For Xenon trioxide, $Xe{O}_3$, let’s calculate the number of electron pairs.
- Xenon has 8 valence electrons and oxygen has 6 valence electrons.
- Therefore, $8+(3\times 6)={\displaystyle \frac{26}{2}}=13$ electron pairs. So, $Xe{O}_3$ has 13 electron pairs present in it.
- Let’s draw the Lewis structure for $Xe{O}_3$.

- In this structure, we can see that all 13 electron pairs are present either as bond-pairs or as lone-pairs.
- Let’s take a look at its hybridization now. Xenon has vacant 5d orbitals so, when xenon gets excited its fifth orbital configuration will become $5s^{2}5p^{3}5d^3$. 5s and 5p orbitals will undergo $s{p}^3$ hybridization.
- Therefore, Xenon in xenon trioxide will have three $s{p}^3$ hybrid orbitals, containing three unpaired electrons and one lone pair of electrons, and unhybridized 5d orbitals having three unpaired electrons.

- Oxygen will undergo $s{p}^2$ hybridization and will have two $s{p}^2$ hybridized orbitals having one lone pair of electrons each and one $s{p}^2$ hybridized orbital containing one unpaired electron. It will have one unhybridized 2p orbital having one electron.

- The three $s{p}^3$ orbitals of xenon having three unpaired electrons will axially overlap with three $s{p}^2$ orbitals of three individual oxygen atoms to form three $\sigma -bonds$. The three 5d orbitals will laterally overlap with three 2p unhybridized orbitals of three oxygen atoms to form three $\pi -bonds$.
- Now, each oxygen atom has two lone pairs of electrons and a xenon atom has one lone pair of electrons. Xenon and oxygen are doubly bonded to each other.

- Due to the presence of lone pair on central atom Xenon, there will be lone pair-bond pair repulsion in the molecule. So, the trigonal planar geometry will be distorted to form pyramidal geometry.

- Therefore, the geometry of $Xe{O}_3$ is pyramidal.
So, the correct answer is “Option C”.

Note: Remember when there is a lone pair present on the central atom, there will be lone pair- bond pair repulsion between the central atom and the other atoms linked to it. This will lead to distortion of geometry. Xenon trioxide is an unstable compound and it is a very powerful oxidizing agent.