From your models of SF4, BrF3 and XeF4, deduce whether different atom arrangements,called geometrical isomers,arepossible,and,ifso,sketch them below.indicate the preferred geometry for each case and suggest a reason for your choice. indicate which structures have dipole moments,and show their direction.
MOLECULE DIPOLE MOMENT PREFERRED GEOMETRY REASON
A) SF4
B) BrF3
C) XeF4
The correct answer and explanation is :
A) SF4 (Sulfur Tetrafluoride)
Preferred Geometry: See-Saw (Trigonal Bipyramidal)
Dipole Moment: Yes, the molecule has a dipole moment. The dipole moment is directed from the sulfur atom towards the fluorine atoms.
Reasoning: SF4 has five electron pairs around the central sulfur atom, including one lone pair, making it a trigonal bipyramidal structure. This lone pair occupies an equatorial position, leading to a see-saw geometry. The fluorine atoms are highly electronegative, and the asymmetry in the molecule causes a net dipole moment. This is because the positions of the fluorine atoms do not cancel out the individual dipole moments of the bonds.
B) BrF3 (Bromine Trifluoride)
Preferred Geometry: T-Shaped (Trigonal Bipyramidal)
Dipole Moment: Yes, the molecule has a dipole moment. The dipole moment is directed from the bromine atom towards the fluorine atoms.
Reasoning: BrF3 has five electron pairs around the central bromine atom, with two of them being lone pairs. This results in a trigonal bipyramidal structure, where the fluorine atoms occupy the equatorial positions, and the lone pairs occupy the axial positions. The resulting geometry is T-shaped. Due to the polar nature of the Br-F bonds and the asymmetry in the arrangement of fluorine atoms, the molecule exhibits a dipole moment. The dipole moment points towards the fluorine atoms, as they are more electronegative than bromine.
C) XeF4 (Xenon Tetrafluoride)
Preferred Geometry: Square Planar
Dipole Moment: No, the molecule does not have a dipole moment.
Reasoning: XeF4 has six electron pairs around the central xenon atom, with two of them being lone pairs. The structure is square planar, as the lone pairs occupy opposite positions, minimizing repulsion and creating a symmetrical arrangement. The fluorine atoms are arranged symmetrically around the xenon atom. Since the geometry is symmetrical, the individual dipoles of the Xe-F bonds cancel out, resulting in no net dipole moment.
Summary Table:
| Molecule | Dipole Moment | Preferred Geometry | Reason |
|---|---|---|---|
| SF4 | Yes | See-Saw (Trigonal Bipyramidal) | Asymmetric arrangement of electronegative fluorine atoms causes a net dipole. |
| BrF3 | Yes | T-Shaped (Trigonal Bipyramidal) | Asymmetry and polar bonds lead to a dipole moment. |
| XeF4 | No | Square Planar | Symmetrical arrangement cancels out the dipole moments. |
Explanation:
- SF4 has a net dipole moment due to its asymmetrical shape (see-saw) and highly electronegative fluorine atoms, creating a difference in electron distribution.
- BrF3 has a T-shaped structure due to lone pairs on the bromine, leading to asymmetry and a dipole moment pointing towards the fluorine atoms.
- XeF4 has a square planar structure with no dipole moment due to the symmetry of the molecule, where all the bond dipoles cancel each other out.
These observations are based on the electron domain theory, the nature of fluorine’s electronegativity, and the geometric arrangement of atoms in each molecule.