Question

question 6
which of the following incorrectly assigns a dipole moment to a bond?
o d+br-br d-
o d+si-s d-
o d+h-f d-
o d+h-cl d-
1 pts

Explanation:

A dipole moment occurs in a bond when there is a significant difference in electronegativity between the two atoms forming the bond. The direction of the dipole moment is from the less electronegative atom (partial positive, $\delta +$) to the more electronegative atom (partial negative, $\delta -$).

• In $H - Cl$, $Cl$ is more electronegative than $H$, so the dipole moment should be $H^{\delta +}-Cl^{\delta -}$, not $H^{\delta -}-Cl^{\delta +}$.
• In $H - F$, $F$ is more electronegative than $H$, so $H^{\delta +}-F^{\delta -}$ is correct.
• In $Si - S$, $S$ is more electronegative than $Si$, so $Si^{\delta +}-S^{\delta -}$ is correct.
• In $Br - Br$, since both atoms are the same (same electronegativity), there is no dipole moment. But if we consider the notation for a non - polar bond (even though the dipole moment is zero in a strict sense for identical atoms), the equal sharing implies no $\delta +$ or $\delta -$ separation. However, compared to the incorrect $H - Cl$ notation, the $H - Cl$ option wrongly assigns the partial charges.

Answer:

$H^{\delta -}-Cl^{\delta +}$ (the first option) is incorrect in assigning the dipole moment.