Question

$H_{2}O$ is dipolar, whereas $Be{F}_2$ is not. It is because

• A. The electronegativity of F is greater than that of O
• B. $H_{2}O$ involved hydrogen bonding whereas $Be{F}_2$ is a discrete molecule
• C. $H_{2}O$ is linear and $Be{F}_2$ is angular
• D. $H_{2}O$ is angular and $Be{F}_2$ is linear

Answer 1

The correct option is D $H_{2}O$ is angular and $Be{F}_2$ is linear

Let's look at $H_{2}O$.

Number of electron pairs = $\frac{6+2}{2}=4$

But there are only 2 hydrogen bonds, so the remaining 2 electron pairs will be lone pairs. So the final shape will be kind of like a bent line. If you look at the dipole moment and the direction given below, you can easily see that the vector addition will not be 0. So, this molecule will have some dipole moment.



Let's look at $Be{F}_2$

Number of electron pairs = $\frac{2+2}{2}=2$

And we have 2 fluorine atoms for bonding. So both these electron pairs will be bonded and there will be no lone pairs.

The shape will be linear. But the net dipole moment will be 0 as the moments are exactly opposite in direction.