Multiple Choice
Which of the following Lewis structures best represents a polar molecule?
13. Liquids, Solids & Intermolecular Forces
Molecular Polarity
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Which of the following best describes the molecular polarity of SiCl_4?
A
SiCl_4 is a polar molecule because the Si-Cl bonds are polar and the molecule has an asymmetrical shape.
B
SiCl_4 is a nonpolar molecule because all the Si-Cl bonds are nonpolar.
C
SiCl_4 is a polar molecule because it contains polar bonds and a lone pair on the central atom.
D
SiCl_4 is a nonpolar molecule because its tetrahedral geometry leads to a symmetrical distribution of charge.
Verified step by step guidance1
Identify the molecular geometry of SiCl_4. Silicon (Si) is the central atom bonded to four chlorine (Cl) atoms, and there are no lone pairs on the silicon atom. This arrangement corresponds to a tetrahedral geometry.
Determine the polarity of each Si-Cl bond. Since chlorine is more electronegative than silicon, each Si-Cl bond is polar, with a dipole moment pointing from Si to Cl.
Analyze the symmetry of the molecule. In a tetrahedral geometry, the four polar bonds are symmetrically arranged around the central atom, causing the individual bond dipoles to cancel each other out.
Conclude the overall molecular polarity. Because the bond dipoles cancel due to the symmetrical shape, the molecule has no net dipole moment and is therefore nonpolar.
Summarize the reasoning: Although SiCl_4 contains polar bonds, its symmetrical tetrahedral shape leads to a nonpolar molecule due to the cancellation of dipole moments.
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