Question

Which of the possible molecule/species is having maximum values for dipole moment (where "A" is the central atom) ?

• A. $A{X}_3$ (having one lone pair on central atom)
• B. $A{X}_4$ (tetrahedral)
• C. $A{X}_{4}Y$ (having no lone pair on central atom)
• D. cannot be predicted

Answer 1

Answer: (D)

cannot be predicted

Consider the following options:-
A) $A{X}_3$- Since it has one lone pair on the central atom, it is trigonal pyramidal in shape. The effect of dipole moments due to the $3$ atoms of $X$ will cancel out when added, but the lone pair's effect will remain.
B) $A{X}_4$ - Since it is tetrahedral, the dipole moment is zero.
C) $A{X}_{4}Y$- It is trigonal bipyramidal in shape. The dipole moment is non zero as the vectors do not cancel out since there is a $Y$ atom.
Hence from the options we notice that the dipole moment cannot be predicted.