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

• A. HI
• B. HBr
• C. HCl
• D. HF

Answer: (D)

Verified step by step guidance

1. Understand that the dipole moment (\(\mu\)) of a diatomic molecule depends on two factors: the magnitude of the charge separation and the distance between the charges. It is given by the formula \(\mu = q \times r\), where \(q\) is the magnitude of the partial charges and \(r\) is the bond length.
2. Recognize that the partial charges arise due to differences in electronegativity between the two atoms. The greater the difference in electronegativity, the larger the partial charges and thus the larger the dipole moment.
3. Compare the electronegativities of the halogen atoms involved: Fluorine (F), Chlorine (Cl), Bromine (Br), and Iodine (I). Fluorine is the most electronegative, followed by chlorine, bromine, and iodine.
4. Consider the bond lengths: as the size of the halogen atom increases from F to I, the bond length increases. However, the effect of electronegativity difference is usually more significant than bond length in determining dipole moment.
5. Conclude that HF has the largest dipole moment because it has the greatest electronegativity difference between H and F, resulting in the largest charge separation, despite having the shortest bond length.