Of the molecules below, only ________ is polar.

• A. CO_2
• B. CH_4
• C. CCl_4
• D. NH_3

Answer: (D)

Verified step by step guidance

1. Identify the molecular geometry of each molecule listed: CO_2, CH_4, CCl_4, and NH_3. Molecular geometry affects the distribution of charge and thus polarity.
2. Recall that CO_2 is linear, CH_4 is tetrahedral, CCl_4 is tetrahedral, and NH_3 is trigonal pyramidal due to the lone pair on nitrogen.
3. Understand that polarity depends on both the presence of polar bonds and the molecular shape. Symmetrical molecules tend to be nonpolar because the bond dipoles cancel out.
4. Analyze each molecule: CO_2 has polar bonds but is linear and symmetrical, so it is nonpolar; CH_4 and CCl_4 are symmetrical tetrahedral molecules with nonpolar overall character; NH_3 has a lone pair creating an asymmetrical shape, resulting in a net dipole moment.
5. Conclude that NH_3 is polar because its trigonal pyramidal shape causes an uneven distribution of electron density, making it the only polar molecule among the options.