Which of the following molecules has a permanent electric dipole moment?

• A. CO
• B. CCl_4
• C. O_2
• D. N_2

Answer: (A)

Verified step by step guidance

1. Understand that a permanent electric dipole moment occurs in molecules where there is an uneven distribution of electron density, typically due to differences in electronegativity between atoms and an asymmetrical molecular geometry.
2. Analyze each molecule's structure and symmetry: CCl_4 is tetrahedral and symmetrical, O_2 and N_2 are diatomic molecules with identical atoms, so their electron distribution is symmetrical.
3. Recognize that CO is a diatomic molecule composed of two different atoms (carbon and oxygen) with different electronegativities, leading to an uneven electron distribution.
4. Conclude that because CO has a difference in electronegativity and is a linear molecule with two different atoms, it has a permanent dipole moment.
5. Summarize that molecules with identical atoms or symmetrical geometry (like CCl_4, O_2, and N_2) do not have a permanent dipole moment, while heteronuclear diatomic molecules like CO do.