Introduction
Sir William Ramsay received the Nobel prize in 1904 in Chemistry for discovering “Noble Gasses”. These are also called inert gasses as they do not react easily or react rarely. Xenon is one of the inert gasses and due to its stable electronic configuration, it rarely forms compounds with other elements. Although if we compare it with other inert gasses, due to its large size it is more reactive than those and forms bonds with other elements.
Xenon difluoride is a compound of xenon and fluorine. It is a powerful fluorinating agent composed of one xenon atom and two fluorine atoms. It is one of the most stable xenon compounds. It is a dense white crystalline solid. It is believed that it was probably 1st created by German Chemist Rudolf Hoppe in early 1962. He created it by mixing fluorine and xenon in an electrical discharge. Although the 1st published report of xenon difluoride came in October 1962 by Chernick, et al.
Xenon is a Noble Gas, but It Forms the XeF2 Compound, Why?
You must be having this question in mind as xenon is an inert gas and inert gasses don’t react. Yeah, xenon is an inert gas and has a stable electronic configuration with filled outermost orbitals. But its inner electrons screen the outer electrons from the nucleus as xenon is a large size element. So, its outermost electrons experience a weaker attraction force to the nucleus.
Highly electronegative and small-sized elements target the outermost electrons of xenon. Hence, valence electrons of xenon get attracted by fluorine and they get bonded.
Bonding in XeF2
It was earlier believed that noble gasses could not react at all but the production of the first true chemical compound with xenon immediately raised lots of questions. This compound was XePtF6 and it made people wonder whether the previous models of bonding were still valid. After due research was carried out, it became clear that the same models can be applied both for interhalogen and halogen oxy species. Two methods of bonding were explained. These were:
The molecular orbital model and
The valence shell electron pair repulsion scheme.
Structure of Xenon Difluoride
To understand the structure of xenon difluoride you need to know the electronic configuration of xenon and fluorine. Electronic configuration of xenon – Kr 4d10 5s2 5p6 Outermost electrons at Ground State (Xe) –
At excited state (Xe) – Electronic configuration of fluorine – He 2s2 2p5F–
At excited state, xenon has two unpaired electrons while fluorine has one unpaired electron and needs one electron to get a stable electronic configuration like neon. So, two fluorine atoms get bonded with one xenon atom covalently.
(Image will be Uploaded soon)
Xenon Difluoride (XeF2)Xenon has 8 valence electrons. Out of which 2 electrons form sigma bonds with fluorine atoms while the remaining 6 electrons remain as 3 lone pairs. It shows hybridization sp3d as at excited state of xenon you can see ones, 3 -p and one d orbitals are taking place in hybridization. You can also calculate its hybridization by the number of sigma bonds and lone pairs in xenon.
As in sp3d hybridization, two hybridizations are involved – sp2 and PD. Sp2 forms equatorial bonds while PD forms axial bonds. Percentage of s- character in sp2 is 33.33% while in PD it is zero. As there is tremendous repulsion between the lone pairs so they get placed at larger bond angles which are possessed by equatorial bonds (120°). So, lone pairs of xenon get placed at equatorial positions i.e. vertices of the triangle. While fluorine atoms get placed at axial position. Thus, the shape of XeF2 is linear and the geometry is trigonal bipyramidal.
Linear Synthesis of Xenon Difluoride
It is synthesized by the reaction of xenon and fluorine gasses in presence of heat, irradiation, or an electrical discharge. Thus, obtained xenon difluoride is solid. It is purified by fractional distillation or selective condensation using a vacuum duct. (Image to be added soon)It can also be synthesized by dioxygen difluoride.
Properties of Xenon Difluoride
XeF2 is soluble in solvents such as BrF5, BrF3, anhydrous hydrogen fluoride, methyl cyanide and IF5. Its molar mass is 169.290 g.mol-1.
It is the most stable xenon compound. It is moisture sensitive. It releases toxic compounds in contact with moisture. It decomposes in contact with light or water vapor.
It is a dense, white coloured crystalline solid. It has a nauseating odor and low vapor pressure. Its melting point is 128.6℃. It is corrosive to exposed tissues. Its shape is linear. It is soluble in water. Solubility in water is 25g/L at 0℃.
The xe-F bond length in solid xenon difluoride is 200 picometre while in vapor state it is 197.73 picometre.
Applications of Xenon Difluoride
Few applications of XeF2 are listed below –
It is used as a strong fluorinating agent.
It works as an oxidizing agent as well.
It is used as an isotropic gaseous etchant for silicon particularly in the production of microelectromechanical systems.
It has a high etch rate and does not require external energy or ion bombardment for the etching of silicon.
It is used to analyze sulfur, selenium and tellurium in the number of compounds.
It is also used for the detection and determination of the amount of iodine.
Its reaction with uracil is used for the production of the anticancer drug 5-fluorouracil.
Caution must be taken while using XeF2 as when it reacts with moisture it produces toxic and explosive substances.
This was all about Xenon difluoride, if you are looking for solutions to NCERT problems related to XeF2, then log on to the Vedantu website or download Vedantu Learning App. By doing so, you will be able to access free PDFs of NCERT Solutions as well as Revision notes, Mock Tests and much more.
FAQs on Xenon Difluoride
1. What is Xenon Difluoride?
Xenon Difluoride, with the chemical formula XeF2, is a chemical compound of xenon and fluorine. It is one of the most stable xenon compounds and presents as a dense, white crystalline solid. Despite xenon being a noble gas, it can react with highly electronegative elements like fluorine under specific conditions to form such compounds.
2. How is Xenon Difluoride typically prepared?
The most common method for preparing Xenon Difluoride involves the direct reaction of its constituent elements. A mixture of xenon (Xe) and fluorine (F₂) gases, typically in a 2:1 ratio, is heated to around 400°C in a sealed nickel vessel. The reaction can also be initiated using irradiation or an electrical discharge, resulting in the formation of solid XeF₂.
3. What is the hybridization and molecular geometry of XeF2?
The central xenon atom in XeF₂ undergoes sp³d hybridization. This results in a trigonal bipyramidal electron geometry. The xenon atom has 8 valence electrons, with 2 forming bonds with fluorine and the remaining 6 existing as 3 lone pairs.
4. How does VSEPR theory explain the linear shape of Xenon Difluoride?
According to the VSEPR (Valence Shell Electron Pair Repulsion) theory, the electron pairs arrange themselves to minimize repulsion. In XeF₂'s trigonal bipyramidal geometry, the three lone pairs occupy the equatorial positions to be farthest apart (120° angles). This forces the two fluorine atoms into the axial positions, resulting in a linear molecular shape with an F-Xe-F bond angle of 180°.
5. What are the key physical and chemical properties of Xenon Difluoride?
- Physical Properties: It is a dense, white crystalline solid with a nauseating odour and a low vapour pressure. Its melting point is 128.6°C.
- Chemical Properties: XeF₂ is the most stable of the xenon compounds. However, it is sensitive to moisture and decomposes when it comes into contact with water vapour or light. It is a powerful fluorinating agent.
6. What are the important applications of Xenon Difluoride?
Xenon Difluoride has several key industrial and laboratory applications, such as:
- Acting as a strong fluorinating and oxidizing agent in chemical synthesis.
- Used as an isotropic gaseous etchant for silicon in the production of Micro-Electro-Mechanical Systems (MEMS).
- Its reaction with uracil is used to produce the anticancer drug 5-fluorouracil.
- It is also used in the analysis of sulfur, selenium, tellurium, and iodine in various compounds.
7. Why was the discovery of xenon compounds so significant in chemistry?
The discovery of xenon compounds like XeF₂ was revolutionary because it disproved the long-held belief that noble gases were completely 'inert' and could not form chemical bonds. The synthesis of the first true noble gas compound, XePtF₆, and later XeF₂, forced chemists to re-evaluate and expand existing models of chemical bonding to accommodate these hypervalent molecules, where an atom appears to have more than eight electrons in its valence shell.
8. What happens when Xenon Difluoride reacts with water?
Xenon Difluoride reacts with water in a process called hydrolysis. It decomposes to produce xenon gas, hydrogen fluoride (HF), and oxygen. The reaction is: 2XeF₂(s) + 2H₂O(l) → 2Xe(g) + 4HF(aq) + O₂(g). Because hydrogen fluoride is toxic and corrosive, this reaction highlights the need for careful handling of XeF₂ away from moisture.
9. How does the structure of XeF₂ compare with other xenon fluorides like XeF₄ and XeF₆?
The structures of xenon fluorides change as more fluorine atoms are added:
- XeF₂: Has 2 bond pairs and 3 lone pairs, resulting in a linear shape.
- XeF₄: Has 4 bond pairs and 2 lone pairs, resulting in a square planar shape.
- XeF₆: Has 6 bond pairs and 1 lone pair, resulting in a distorted octahedral shape.
