Concept: Molecular polarity is determined by both the polarity of individual bonds and the molecular geometry. A molecule is non-polar if the vector sum of all bond dipoles is zero. This typically occurs when the molecule has a symmetrical structure, even if individual bonds are polar.

Why (A) is correct:

Methane (CH₄):

• The central carbon atom is sp³ hybridized, leading to a tetrahedral geometry.
• The C-H bonds are slightly polar due to the difference in electronegativity between carbon and hydrogen.
• However, due to the perfectly symmetrical tetrahedral arrangement, the four C-H bond dipoles cancel each other out.
• Therefore, methane (CH₄) is a non-polar molecule.

Option Analysis:

• A) CH₄: Tetrahedral geometry, symmetrical distribution of polar C-H bonds, resulting in a net dipole moment of zero. Hence, non-polar.
• B) SO₂: Sulfur dioxide has a bent molecular geometry due to the presence of one lone pair on the central sulfur atom (sp² hybridization). The S-O bonds are polar, and their dipoles do not cancel out, leading to a net dipole moment. Hence, polar.
• C) NF₃: Nitrogen trifluoride has a trigonal pyramidal geometry due to the presence of one lone pair on the central nitrogen atom (sp³ hybridization). The N-F bonds are polar, and their dipoles do not cancel out, leading to a net dipole moment. Hence, polar.
• D) SF₄: Sulfur tetrafluoride has a seesaw geometry due to the presence of one lone pair on the central sulfur atom (sp³d hybridization). The S-F bonds are polar, and their dipoles do not cancel out due to the asymmetrical arrangement, leading to a net dipole moment. Hence, polar.

Correct Answer: (A)