In molecular structure, the carbon tetrachloride molecule (CCl4) has which combination of overall molecular polarity and individual bond polarity?

Introduction / Context:
This question examines your understanding of molecular polarity versus bond polarity in covalent compounds. Students often learn how to predict whether a bond is polar by comparing electronegativities and then must extend that understanding to decide if the entire molecule is polar or nonpolar based on its geometry. Carbon tetrachloride, CCl4, is a classic textbook example where each bond is polar but the overall molecule is nonpolar due to its highly symmetric shape.

Given Data / Assumptions:

• The molecule under discussion is CCl4, carbon tetrachloride.
• Carbon is at the centre with four chlorine atoms attached.
• Electronegativities of carbon and chlorine are different, so individual bonds may be polar.
• The geometry around carbon in CCl4 is tetrahedral.
• The options describe combinations of molecular polarity and bond polarity.

Concept / Approach:
Bond polarity arises when two atoms in a covalent bond have different electronegativities, causing unequal sharing of electrons and creating a dipole. Molecular polarity depends on both the polarity of individual bonds and the three dimensional geometry of the molecule. In a perfectly symmetric molecule, the individual bond dipoles can cancel vectorially, resulting in no net dipole moment. In CCl4, carbon and chlorine form polar covalent bonds because chlorine is more electronegative than carbon. However, with four identical C–Cl bonds arranged in a regular tetrahedron, the dipoles cancel out, producing an overall nonpolar molecule. Thus, CCl4 has polar bonds but is itself nonpolar.

Step-by-Step Solution:
Step 1: Compare electronegativities. Chlorine is more electronegative than carbon, so each C–Cl bond is polar with a partial negative charge on chlorine. Step 2: Determine the molecular geometry. With four bonding pairs and no lone pairs around carbon, VSEPR theory predicts a tetrahedral shape for CCl4. Step 3: Visualise the four C–Cl bond dipoles pointing from the central carbon out toward the chlorine atoms. Step 4: Because the molecule is perfectly symmetrical, the vector sum of the four bond dipoles is zero. Step 5: A zero resultant dipole moment means the molecule as a whole is nonpolar, even though individual bonds are polar. Step 6: Therefore CCl4 is a nonpolar molecule with polar C–Cl bonds.

Verification / Alternative check:
Empirically, CCl4 is insoluble in water but dissolves many nonpolar substances like oils and fats, which is typical behaviour of nonpolar solvents. At the same time, its boiling point and intermolecular forces are higher than those of truly nonpolar molecules like methane, partly because the polarizable C–Cl bonds contribute to stronger dispersion and induced interactions. This combination of properties supports the view that C–Cl bonds have significant polarity, but the molecular symmetry eliminates any net permanent dipole. Comparing CCl4 with CHCl3 (chloroform), where one hydrogen replaces a chlorine and breaks perfect symmetry, also shows that CHCl3 is polar, while CCl4 is not.

Why Other Options Are Wrong:
Option B claims that both the molecule and its bonds are nonpolar, which is incorrect because C–Cl bonds are known to be polar due to electronegativity difference. Option C states that the molecule is polar, which would require a net dipole moment and asymmetry, not present in tetrahedral CCl4. Option D suggests a polar molecule with nonpolar bonds, which is conceptually inconsistent because molecular polarity arises from bond dipoles and geometry. Option E introduces the idea of an ionic molecule, which does not apply here; CCl4 is a covalent compound, not an ionic salt.

Common Pitfalls:
A frequent mistake is to assume that if all bonds in a molecule are polar, then the molecule must be polar. This ignores the crucial role of geometry and vector cancellation of dipoles. Another error is confusing the terms polar bond and polar molecule, using them interchangeably. To avoid this, always perform two checks: first for bond polarity using electronegativities, and then for molecular polarity using shape and symmetry. Remember that highly symmetric molecules such as CO2 (linear) and CCl4 (tetrahedral) often turn out to be nonpolar despite having polar bonds.

Final Answer:
Carbon tetrachloride, CCl4, is a nonpolar molecule with polar C–Cl bonds.