(a) Consider the following two molecules: PCl3 and BCl3. Which molecule has a nonzero dipole mom

step 1 The best way to determine whether there's a dipole moment or not is to draw the Lewis structures

(a) Consider the following two molecules: PCl3 and BCl3....

(a) Consider the following two molecules: $\mathrm{PCl}_{3}$ and $\mathrm{BCl}_{3}$. Which molecule has a nonzero dipole moment?
(b) Consider the following two molecules: $\mathrm{XeF}_{4}$ and $\mathrm{SF}_{4}$. Which molecule has a zero dipole moment?

Key Concepts

VSEPR Theory

Valence Shell Electron Pair Repulsion (VSEPR) theory explains the shapes of molecules based on the repulsions between electron pairs, both bonding and non-bonding, around a central atom. This theory helps predict whether the geometry of a molecule will be symmetrical or asymmetrical, which in turn influences the net dipole moment of the molecule.

Symmetry and Dipole Moment Cancellation

Symmetry in molecular structures plays a pivotal role in determining overall polarity. Molecules with high symmetry can arrange their polar bonds in such a way that the individual bond dipoles cancel out, resulting in a zero net dipole moment. Conversely, asymmetric arrangements, often due to the presence of lone pairs or non-uniform bonding, can lead to a nonzero net dipole moment.

Molecular Geometry

Molecular geometry refers to the three-dimensional arrangement of atoms within a molecule. This concept is critical for understanding the net dipole moment because the spatial distribution of polar bonds, especially when influenced by lone pairs, determines whether the individual bond dipoles cancel out or reinforce each other to create an overall molecular polarity.

Bond Polarity and Electronegativity

Bond polarity arises from differences in electronegativity between atoms, creating regions of partial positive and partial negative charge. Understanding how these polar bonds form and contribute to a molecule's electrical asymmetry is essential when analyzing whether a molecule will exhibit a net dipole moment.

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