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 polarity of the individual bonds contribute to a net dipole moment that is nonzero.
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. The presence of this lone pair affects the molecular shape, pushing the bonded atoms downward and resulting in a trigonal pyramidal structure. This is similar to the geometry of ammonia (NH₃), where the lone pair distorts an otherwise tetrahedral arrangement.
The dipole moment arises from differences in electronegativity between bonded atoms. Fluorine is the most electronegative element, and oxygen is also highly electronegative, although slightly less so than fluorine. Selenium, being less electronegative than both, allows for polar bonds between Se and O as well as Se and F. Each of these bonds has a dipole pointing from selenium toward the more electronegative atom.
Due to the trigonal pyramidal shape, these bond dipoles do not cancel out. If the molecule were symmetrical — such as in a trigonal planar shape — the bond dipoles might cancel depending on orientation. However, the lone pair on selenium distorts the molecule out of a planar configuration, preventing the dipoles from balancing one another.
The result is a net molecular dipole that points away from selenium toward the region between the oxygen and fluorine atoms. This net dipole means that SeOF₂ is a polar molecule with a nonzero dipole moment. The asymmetrical geometry combined with polar bonds ensures that the molecule as a whole has a separation of charge, which is what defines a dipole moment. Thus, the trigonal pyramidal geometry and the polarity of the Se–O and Se–F bonds are directly responsible for the observed dipole moment.
