Question

Evaluate potential energy per ion for NaCl crystal. Use inter atomic spacing $2.82\times {10}^{10}m$.

• A. $8.12\times {10}^{-19}J$
• B. $2.67\times {10}^{-19}J$
• C. $5.67\times {10}^{-19}J$
• D. none

Answer 1

The correct option is A $8.12\times {10}^{-19}J$

Given inter atomic distance , $d=2.82\times {10}^{-10}m$.

Potential energy per ion in 3-dimensional for NaCl crystal is $U=\frac{+e(-e)}{4\pi {ϵ}_{0}d}$

or $U=-\frac{(1.6\times {10}^{-19}{)}^2}{4\times 3.14\times 8.85\times {10}^{-12}\times 2.82\times {10}^{-10}}=-8.16\times {10}^{-19}J$