The xef2 lewis structure places xenon in the center with two single Xe–F bonds and three lone pairs on Xe, giving five electron domains around the central atom. That electron-domain arrangement is trigonal-bipyramidal, while the molecular shape is linear because the three lone pairs occupy equatorial positions.
Valence-electron count and skeletal connectivity
XeF2 contains one xenon atom and two fluorine atoms. The total number of valence electrons is obtained from the group numbers:
\[ \text{valence e}^- = 8 \;(\text{Xe}) + 2 \times 7 \;(\text{F}) = 22 \]
Xenon is the least electronegative atom in the formula and serves as the central atom in the Lewis picture, with two fluorine atoms terminal. Two Xe–F single bonds account for \(2 \times 2 = 4\) electrons, leaving \(22 - 4 = 18\) electrons to distribute as lone pairs.
Lewis structure: lone pairs, octets, and formal charge
Each fluorine completes its octet with three lone pairs (6 electrons each). Two fluorine atoms therefore take \(2 \times 6 = 12\) electrons as lone pairs, leaving \(18 - 12 = 6\) electrons on xenon as lone pairs, i.e., three lone pairs.
Electron-domain summary on XeAX2E3
Two bonding domains (two Xe–F bonds) and three lone-pair domains give a total of five electron domains around xenon.
Formal charges verify the most stable Lewis assignment (all atoms carry 0 formal charge). Using \[ \text{FC} = V - \left(N + \frac{B}{2}\right), \] for xenon \(V = 8\), \(N = 6\) (three lone pairs), and \(B = 4\) (two single bonds), so \[ \text{FC(Xe)} = 8 - \left(6 + \frac{4}{2}\right) = 8 - (6 + 2) = 0. \] For each fluorine \(V = 7\), \(N = 6\), \(B = 2\), so \[ \text{FC(F)} = 7 - \left(6 + \frac{2}{2}\right) = 7 - (6 + 1) = 0. \]
VSEPR: electron geometry versus molecular geometry
Five electron domains adopt a trigonal-bipyramidal electron-domain arrangement. In that arrangement, equatorial positions experience fewer 90° interactions than axial positions, so the three lone pairs preferentially occupy the equatorial sites. The two Xe–F bonding pairs then lie opposite one another along the axial line, giving a linear molecular geometry with an F–Xe–F angle of approximately \(180^\circ\).
| Feature | Result for XeF2 | Interpretation |
|---|---|---|
| Total valence electrons | 22 | Electron bookkeeping for the Lewis framework |
| Central-atom domains | 5 (2 bonds + 3 lone pairs) | VSEPR class AX2E3 |
| Electron-domain geometry | Trigonal bipyramidal | Arrangement of all domains around Xe |
| Molecular geometry | Linear | Shape traced by the atoms (ignoring lone pairs) |
| Formal charges | 0 on all atoms | Most stable Lewis structure assignment |
Polarity and dipole cancellation
Each Xe–F bond is polar because fluorine is much more electronegative than xenon. However, the linear geometry places the two equal bond dipoles in opposite directions, so they cancel. The molecule is therefore nonpolar overall, despite having polar bonds.
Common pitfalls
A frequent error is assigning the three lone pairs on xenon to axial positions, which would create excessive 90° lone-pair interactions and contradict the VSEPR preference for equatorial lone pairs in a trigonal-bipyramidal electron arrangement. Another error is forcing multiple bonds to fluorine; fluorine rarely forms stable multiple bonds in typical Lewis-structure treatments, and doing so disrupts octet completion and formal-charge minimization.