Which of the following diatomic molecules has the smallest dipole moment?

• A. N_2
• B. HF
• C. HCl
• D. CO

Answer: (A)

Verified step by step guidance

1. Recall that the dipole moment of a molecule depends on the difference in electronegativity between the two atoms and the bond length. The greater the difference in electronegativity, the larger the dipole moment, assuming bond length is similar.
2. Identify the electronegativity values of the atoms in each diatomic molecule: for example, H (2.1), F (4.0), Cl (3.0), C (2.5), O (3.5), and N (3.0).
3. Calculate or estimate the electronegativity difference for each molecule: HF, HCl, CO, and N₂. For example, HF has a large difference (4.0 - 2.1), while N₂ has zero difference since both atoms are the same.
4. Understand that homonuclear diatomic molecules like N₂ have no net dipole moment because the electron distribution is symmetrical, resulting in a dipole moment of zero or very close to zero.
5. Conclude that among the given molecules, N₂ has the smallest dipole moment due to its identical atoms and symmetrical electron distribution.