What is the electron geometry of BrF5?
2. What is the molecular geometry of BrF5?
3. Which choice best describes the polarity of BrF5?
a. The molecule is polar and has polar bonds.
b. The molecule is nonpolar and has polar bonds.
c. The molecule is polar and has nonpolar bonds.
d. The molecule is nonpolar and has nonpolar bonds.
The Correct Answer and Explanation is:
- Electron Geometry of BrF₅:
The electron geometry of BrF₅ (bromine pentafluoride) is octahedral. This is because the central bromine atom is surrounded by six regions of electron density: five bonding pairs (from the five fluorine atoms) and one lone pair. According to VSEPR (Valence Shell Electron Pair Repulsion) theory, six regions of electron density around a central atom correspond to an octahedral electron geometry. - Molecular Geometry of BrF₅:
The molecular geometry of BrF₅ is square pyramidal. Although the electron geometry is octahedral, the presence of one lone pair on the central bromine atom distorts the shape, resulting in a square pyramidal molecular geometry. This means the bromine is at the center, four fluorine atoms form a square base, and the fifth fluorine occupies the apex position. - Polarity of BrF₅:
Correct answer: a. The molecule is polar and has polar bonds.
Explanation
BrF₅ (bromine pentafluoride) is an interhalogen compound where bromine is the central atom surrounded by five fluorine atoms and one lone pair. To determine its electron and molecular geometry, we apply the principles of VSEPR theory. Bromine has seven valence electrons. It forms five single bonds with fluorine atoms, using five electrons, and retains one lone pair. This results in six regions of electron density around the central atom, which corresponds to an octahedral electron geometry.
However, due to the lone pair, the actual molecular geometry becomes square pyramidal. The lone pair occupies one position in the octahedral arrangement, pushing the bonding pairs slightly and distorting the symmetry.
Regarding polarity, each Br–F bond is polar because fluorine is much more electronegative than bromine. In a perfectly symmetrical molecule like octahedral SF₆, these dipoles would cancel out, making the molecule nonpolar. However, in BrF₅, the asymmetrical square pyramidal shape caused by the lone pair leads to an uneven distribution of electron density.
As a result, BrF₅ is a polar molecule. The vector sum of the bond dipoles does not cancel out, producing a net dipole moment. Therefore, BrF₅ has polar bonds and is a polar molecule, making choice (a) the correct description:
“The molecule is polar and has polar bonds.”
