What is the electron group geometry and molecular geometry, respectively, for the molecule XeF2 ?
A. trigonal bipyramidal, linear
B. trigonal bipyramidal, bent
C. tetrahedral, bent
D. octahedral, bent
E. octahedral, linear
The Correct Answer and Explanation is:
The correct answer for the electron group geometry and molecular geometry of the molecule XeF₂ is A. trigonal bipyramidal, linear.
Explanation:
1. Determining Electron Group Geometry:
To determine the electron group geometry of XeF₂ (xenon difluoride), we first need to consider the Lewis structure and the arrangement of electron groups around the central atom, xenon (Xe).
- Valence Electrons: Xenon, a noble gas, has 8 valence electrons. Each fluorine (F) atom contributes 1 electron, resulting in a total of 10 valence electrons (8 from Xe + 2 from the two F atoms).
- Lewis Structure: In the Lewis structure of XeF₂, xenon is the central atom with two fluorine atoms bonded to it. This leaves three lone pairs of electrons on the xenon atom.
- Electron Groups: The total number of electron groups (bonding and lone pairs) around the xenon atom is five: two bonding pairs (from Xe-F bonds) and three lone pairs. According to the VSEPR (Valence Shell Electron Pair Repulsion) theory, five electron groups around a central atom results in a trigonal bipyramidal electron group geometry.
2. Determining Molecular Geometry:
While the electron group geometry is trigonal bipyramidal, the molecular geometry is determined by the positions of the bonded atoms only, disregarding the lone pairs.
- Molecular Geometry: In XeF₂, the three lone pairs occupy the equatorial positions in the trigonal bipyramidal arrangement, while the two fluorine atoms occupy the axial positions. As a result, the spatial arrangement of the fluorine atoms gives the molecule a linear shape.
This means that, although the electron group geometry is trigonal bipyramidal due to the five groups, the molecular geometry is linear because the two fluorine atoms are directly opposite each other with a bond angle of 180 degrees.
In summary, XeF₂ exhibits a trigonal bipyramidal electron group geometry and a linear molecular geometry, making option A the correct choice.