The dipole moment of the SeOF2 molecule (diagram D) is nonzero. Identify its molecular geometry and explain how its geometry and the polarity of its bonds result in a nonzero dipole moment_
The Correct Answer and Explanation is:
The molecular geometry of selenium oxyfluoride (SeOF₂) is trigonal pyramidal. This geometry and the polar nature of the bonds result in a nonzero dipole moment.
Selenium (Se) is the central atom in SeOF₂, bonded to one oxygen (O) atom and two fluorine (F) atoms, with one lone pair of electrons. Selenium belongs to group 16 and has six valence electrons. In SeOF₂, three of these electrons are used for bonding with oxygen and fluorine atoms, and the remaining two form a lone pair. The presence of this lone pair influences the molecular geometry.
According to the Valence Shell Electron Pair Repulsion (VSEPR) theory, the electron pairs around the central atom will arrange themselves to minimize repulsion. With three bonding regions and one lone pair, the molecular geometry adopts a trigonal pyramidal shape. This is similar to ammonia (NH₃), where the lone pair occupies one of the positions in a tetrahedral arrangement, pushing the bonded atoms downward into a pyramid-like shape.
All the bonds in SeOF₂ are polar because of the difference in electronegativity between selenium and the atoms it is bonded to. Fluorine is much more electronegative than selenium, and oxygen is also more electronegative. This creates bond dipoles pointing from selenium toward both the oxygen and the fluorine atoms.
In a trigonal pyramidal shape, the bond dipoles do not cancel out because they are not arranged symmetrically around the central atom. Instead, their vector sum results in a net dipole moment pointing in a particular direction. If the molecule were symmetrical, such as in a trigonal planar or tetrahedral geometry with identical atoms, the bond dipoles could cancel out, resulting in no net dipole moment. However, the asymmetric shape of SeOF₂ along with the unequal distribution of electronegativity leads to a nonzero dipole moment.
