Which of the following molecules is nonpolar but has polar covalent bonds? — Bonding Chemistry Question

STEPS:

1. Understand the dual criteria of the question: To solve this problem, a student must identify a molecule that satisfies two distinct chemical conditions:
* It must contain polar covalent bonds, which occur when electrons are shared unequally between two nonmetal atoms with different electronegativities.
* The overall molecule must be nonpolar, meaning it has a net dipole moment of zero because its individual bond dipoles cancel each other out due to a highly symmetric molecular geometry.
2. Analyze the bonding and geometry of carbon tetrachloride ($\text{CCl}_4$):
* Bond Polarity: Chlorine ($\text{Cl}$) is significantly more electronegative than carbon ($\text{C}$). Thus, each individual $\text{C}-\text{Cl}$ bond is highly polar covalent, with the electron density pulled strongly toward the chlorine atoms.
* Molecular Geometry: The central carbon atom forms 4 single bonds with no lone pairs, yielding a steric number of 4. This results in an $sp^3$ hybridized carbon with a highly symmetric tetrahedral geometry.
* Molecular Polarity: Because the tetrahedral structure is perfectly symmetrical and all four terminal atoms are identical ($\text{Cl}$), the four equal polar bond dipoles pull outward in opposite directions. These dipoles cancel each other out completely, giving the overall molecule a net dipole moment of zero (nonpolar). This makes Option D the correct answer.

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WHY_OTHERS_WRONG:

• A is incorrect: Nitrogen gas ($\text{N}_2$) is a homonuclear diatomic molecule. Because both nitrogen atoms have identical electronegativities, the electrons in the nitrogen-nitrogen triple bond are shared equally, making the bond nonpolar covalent. It fails the requirement of containing polar covalent bonds.
• B is incorrect: Hydrogen peroxide ($\text{H}_2\text{O}_2$) has an asymmetric, non-planar "open-book" geometry. Because of this lack of symmetry, the polar $\text{O}-\text{H}$ and $\text{O}-\text{O}$ bond dipoles do not cancel out, making the overall molecule polar.
• C is incorrect: Water ($\text{H}_2\text{O}$) has a bent molecular geometry due to the two lone pairs on the central oxygen atom. The individual polar $\text{O}-\text{H}$ bond dipoles do not cancel out, resulting in a strong net dipole moment and making water a highly polar molecule.
• E is incorrect: Dichloromethane ($\text{CH}_2\text{Cl}_2$) has a tetrahedral geometry, but it is highly asymmetric because the central carbon is bonded to two different elements with vastly different electronegativities (hydrogen and chlorine). The strong dipoles of the $\text{C}-\text{Cl}$ bonds are not countered by the weak dipoles of the $\text{C}-\text{H}$ bonds, preventing cancellation and making the overall molecule polar.