Chapter 4: Cohesion between atoms

Example 4.1, page no-92

# Coulomb interatomic energy

import math
#Variable declaration
R=2.81*10**-10                    # distance between oppositely charged ion
e=1.6*10**-19                     # Charge of an electron
eps=8.854*10**-12                 # epsilon

#calculation
U=-(e**2)/(4*math.pi*eps*R)

#Result
print('The Coulomb interatomic energy is %.2f eV'%(U*10**19/1.6))

The Coulomb interatomic energy is -5.12 eV