Question

${\text{BeF}}_2$ has zero dipole moment whereas ${\mathrm{H}}_2\mathrm{O}$ has a dipole moment because:

• A. Water is linear
• B. ${\mathrm{H}}_2\mathrm{O}$ is bent
• C. $\mathrm{F}$ is more electronegative than $\mathrm{O}$
• D. Hydrogen bonding is present in ${\mathrm{H}}_2\mathrm{O}$

Answer 1

The correct option is B

${\mathrm{H}}_2\mathrm{O}$ is bent

Dipole moment:

• When there is a separation of charge, dipole moments happen.
• Dipole moments, which result from variations in electronegativity, can happen between atoms in a covalent link or between two ions in an ionic bond.
• The dipole moment increases with the difference in electronegativity.
• The magnitude of the dipole moment is also affected by the distance between the charge separations.
• The polarity of the molecule is determined by the dipole moment.

Explanation of the correct option:

The correct answer is option B:

• ${\text{BeF}}_2$ has no dipole moment.
• But ${\mathrm{H}}_2\mathrm{O}$ has a non-zero dipole moment.
• Because the presence of lone pairs of electrons bends the structure of ${\mathrm{H}}_2\mathrm{O}$.

Explanation of the incorrect options:

Options A, C, and D:

• Yes, water is linear, $\mathrm{F}$ is more electronegative than $\mathrm{O}$, and Hydrogen bonding is present in ${\mathrm{H}}_2\mathrm{O}$.
• But these are not the reasons for ${\text{BeF}}_2$ has zero dipole moment whereas ${\mathrm{H}}_2\mathrm{O}$ has a dipole moment.

Hence, option B is correct, i.e., ${\mathrm{H}}_2\mathrm{O}$ is bent.