#importing modules
import math
from __future__ import division
#Variable declaration
e=1.602*10**-19; #charge of electron(c)
epsilon0=8.85*10**-12; #permittivity(C/Nm)
r=3*10**-10; #seperation(m)
N=6.022*10**20;
Ea=502; #ionisation energy of A(kJ/mol)
Eb=-335; #electron affinity for B(kJ/mol)
#Calculation
E=-e**2*N/(4*math.pi*epsilon0*r); #electrostatic attraction(kJ/mol)
nE=Ea+Eb+E; #net change in energy per mole(kJ/mol)
#Result
print "net change in energy per mole is",int(nE),"kJ/mol"
print "answer varies due to rounding off errors"
print "since the net change in energy is negative, the A+B- molecule will be stable"
#importing modules
import math
from __future__ import division
#Variable declaration
IPk=4.1; #IP of K(eV)
EACl=3.6; #EA of Cl(eV)
e=1.602*10**-19; #charge of electron(c)
onebyepsilon0=9*10**9;
#Calculation
deltaE=IPk-EACl;
Ec=deltaE; #energy required(eV)
R=e*onebyepsilon0/deltaE; #seperation(m)
#Result
print "energy required is",Ec,"eV"
print "seperation is",round(R*10**9,2),"nm"
#importing modules
import math
from __future__ import division
#Variable declaration
e=1.602*10**-19; #charge of electron(c)
epsilon0=8.85*10**-12; #permittivity(C/Nm)
r0=236*10**-12; #seperation(m)
N=6.022*10**20;
IP=5.14; #ionisation energy of A(kJ/mol)
EA=3.65; #electron affinity for B(kJ/mol)
#Calculation
Ue=-e**2/(4*math.pi*epsilon0*r0*e); #potential energy(eV)
BE=-Ue-IP+EA; #bond energy(eV)
#Result
print "bond energy is",round(BE,2),"eV"
#importing modules
import math
from __future__ import division
#Variable declaration
A=1.748; #madelung constant
n=9; #born repulsive exponent
e=1.602*10**-19; #charge of electron(c)
epsilon0=8.85*10**-12; #permittivity(C/Nm)
r0=0.281*10**-9; #seperation(m)
IE=5.14; #ionisation energy of A(kJ/mol)
EA=3.61; #electron affinity for B(kJ/mol)
#Calculation
CE=A*e**2*(1-(1/n))/(4*math.pi*epsilon0*r0*e); #cohesive energy(eV)
#Result
print "cohesive energy is",round(CE,3),"eV"