Question

The dipole moment of $LiH$ is $1.964\times 10^{-29}$ cm and the interatomic distance between $Li$ and $H$ in this molecule is $1.596\mathring{A}$. The percentage of ionic character in $LiH$ is

• A. $75.0$
• B. $76.8$
• C. $79.8$
• D. $100$

Answer 1

Answer: (B)

The dipole moment of $100\%$ ionic molecule $=\left(1\text{electronic charge}\right)\times \left(\text{interatomic distance}\right)$
$=1.602\times 10^{-19}\times 1.596\times 10^{-10}$
$=2.557\times 10^{-29}cm$
Fractional ionic character $=\frac{\text{Exp. value of dipole moment}}{\text{Theoretical value of dipole moment}}=\frac{1.964\times 10^{-29}}{2.557\times 10^{-29}}$
$=0.768$
The bond in $LiH$ is $76.8\%$ ionic.