Xenon difluoride is a powerful fluorinating agent with the chemical formula XeF ₂, and one of the most stable xenon compounds. Like most covalent inorganic fluorides it is moisture-sensitive. It decomposes on contact with water vapor, but is otherwise stable in storage.
The XeF2 Lewis structure has 5 electron pairs. Out of these 2 electron pairs are bonding pairs as they form a single covalent bond with 2 fluorine atoms and the remaining 3 are lone pairs of electrons.
To draw the Lewis structure for XeF2, follow these steps:
- Count the Valence Electrons:
- Xenon (Xe) is in Group 18, so it has 8 valence electrons.
- Fluorine (F) is in Group 17, so each F has 7 valence electrons, and there are two F atoms, giving us 2 * 7 = 14 electrons.
- Total valence electrons = 8 (from Xe) + 14 (from F) = 22.
- Arrange the Atoms:
- Xe is the central atom because it’s less electronegative than F and can expand its octet.
- Form Chemical Bonds:
- Place two fluorine atoms around Xe. Each bond (a line) represents two electrons.
- Distribute Remaining Electrons:
- Start by placing electrons around the fluorine atoms to complete their octets (remember, F needs only 8 electrons to fulfill the octet rule).
- Each F will have 6 non-bonding electrons plus the 2 shared in the bond with Xe, totaling 8 electrons around each F.
This uses up:- 2 electrons per bond * 2 bonds = 4 electrons
- 6 electrons per F * 2 F = 12 electrons
Total used = 4 (bonds) + 12 (lone pairs on F) = 16 electrons.- Remaining electrons = 22 – 16 = 6. These 6 go on Xe as three lone pairs.
Lewis Structure:
- Here’s how it looks:
Where:
- Each line (-) represents a bond (2 electrons).
- Dots (..) represent lone pairs of electrons.
Check Formal Charges:
- For Xe: It has 8 electrons around it in this structure (2 in bonds and 6 in lone pairs), which matches its valence count, so its formal charge is 0.
- For F: Each F has 7 electrons of its own (6 in lone pairs, 1 in a bond), but one is shared, so effectively, it “owns” 7 electrons. Since its valence is 7, the formal charge for each F is 0.
Hybridization
Count the Electron Domains:
- Xe (Xenon) has 8 valence electrons. In XeF2, two of these electrons are involved in bonds with two F atoms, and there are three lone pairs on Xe.
- Therefore, there are 5 electron domains around Xe (2 bonds + 3 lone pairs).
Determine Hybridization:
- When there are 5 electron domains, the hybridization is sp3d. This means one s orbital, three p orbitals, and one d orbital mix to form five sp3d hybrid orbitals.
Geometry:
VSEPR Theory:
- According to the Valence Shell Electron Pair Repulsion (VSEPR) theory, the geometry of a molecule is determined by the arrangement of electron pairs around the central atom to minimize repulsion.
- Although there are 5 electron domains, the molecular geometry is based only on the atoms bonded to the central atom, not the lone pairs.
Molecular Shape:
- With three lone pairs and two bond pairs, the lone pairs will occupy the equatorial positions in a trigonal bipyramidal arrangement to minimize electron pair repulsion.
- This leaves the two fluorine atoms in the axial positions.
- The resulting shape when considering only the atoms (ignoring the lone pairs) is linear.
Summary
The XeF2 Lewis structure consists of a central xenon atom (Xe) and two external fluorine atoms (F). There are two single bonds between the xenon atom (Xe) and each fluorine atom (F). There are three lone pairs of electrons on the xenon atom (Xe) and on each of the two fluorine atoms (F). The XeF2 Lewis structure is shown below:
- Hybridization: sp3d
- Molecular Geometry: Linear
- The F-Xe-F bond angle is 180 degrees due to the linear arrangement.
Additional Notes:
- Electron Pair Geometry: The electron pair geometry, which includes the lone pairs, is trigonal bipyramidal. Here, the three equatorial positions are occupied by the lone pairs, and the two axial positions by the fluorine atoms.
- Stereochemistry: The presence of three lone pairs not only forces the linear shape but also makes XeF2 one of the classic examples where the central atom in a molecule uses its d-orbitals for hybridization, going beyond the octet rule.