To determine which of these molecules has a dipole moment of zero due to symmetry, we need to analyze their molecular geometries.
- BeI2: This molecule adopts a linear geometry. Since it is linear and the two iodine atoms are identical, their dipole moments cancel each other out. Thus, BeI2 has a net dipole moment of zero.
- TeF4: TeF4 has a seesaw shape due to the presence of one lone pair on the tellurium atom. The difference in electronegativity between tellurium and fluorine results in bond dipoles that do not cancel completely, leading to a non-zero dipole moment.
- TeF6: TeF6 is an octahedral molecule. In this case, all six fluorine atoms are symmetrically arranged around the tellurium atom. The bond dipoles cancel each other out completely, resulting in a dipole moment of zero.
- SeF2: SeF2 has a bent molecular shape due to the presence of lone pairs on selenium. The asymmetry in the arrangement of fluorine atoms leads to a net dipole moment that is not zero.
In summary, the molecules that would be expected to have a dipole moment of zero because of symmetry are BeI2 and TeF6.