Chapter 1: Bonding in Solids

Example 1.1, Page number 1.4

In [19]:
from math import pi

#Variable declartion
E_a = 502        #first ionization energy of A(kJ/mol)
E_b = -335       #electron affinity for B atom(kJ/mol)
d = 3*10**-10    #inter-ionic seperation(m)
E = 8.85*10**-12 #permittivity of free space(C/N -m)
e = 1.602*10**-19#charge of an electron(C)

#Calculations
C_e = (-e**2)/(4*pi*E*d)           #Coulumbic attraction energy(J/ion pair)
C_e_kj = C_e *6.022*10**23*10**-3  #Converting C_e to KJ/mol
n_e = E_a + E_b  + C_e_kj          #Net change in energy per mole

#Results
print "Net change in energy is =",round(n_e,3),"kJ/mol"
print "As the net change in energy is negative, the molecule will be stable"
print "\nThe solution differs because of rounding-off of the digits in the textbook"

Net change in energy is = -296.224 kJ/mol
As the net change in energy is negative, the molecule will be stable

The solution differs because of rounding-off of the digits in the textbook

Example 1.2, Page number 1.4

In [7]:
from math import pi 

#Variable declaration
IP_K = 4.1        #ionization energy of K(eV)
EA_Cl = 3.6       #electron affinity of Cl(eV)
e = 1.602*10**-19 #charge of an electron(C)
Eo = 8.85*10**-12 #permittivity of free space(C/N -m)

#Calcuations
del_E = IP_K - EA_Cl
#Ec = 0.5 = -e/4*pi*Eo*R
R = e/(4*pi*Eo*del_E)

#Results
print "(a) If their total energy is to be zero, then del_E = Ec"
print "(b) The seperation between the ion pair is", round((R/1E-9),2), "nm"

(a) If their total energy is to be zero, then del_E = Ec
(b) The seperation between the ion pair is 2.88 nm

Example 1.3, Page number 1.5

In [9]:
from math import pi

#Variable declaration
ro = 2.36*10**-10  #inter ionic equilibrium distance(m)
IP = 5.14          #ionization energy of Na(eV)
EA = 3.65          #electron affinity of Cl(eV)
e = 1.602*10**-19  #charge of an electron(C)
Eo = 8.85*10**-12  #permittivity of free space(C/N -m)

#Calculations
Ue = (-e**2)/(4*pi*Eo*ro*e) #Potential energy in eV
Be = -Ue - IP + EA

#Result
print "Bond energy for NaCl molecule is",round(Be,2),"eV"

Bond energy for NaCl molecule is 4.61 eV

Example 1.4, Page number 1.18

In [22]:
from math import pi

#Variable declaration
ro = 0.281*10**-9 #equilibrium seperation between the ion pair(m)
IP = 5.14         #ionization energy of Na(eV)
EA = 3.61         #electron affinity of Cl(eV)
A = 1.748         #Madelung constant
n = 9.            #born replusive exponent
e = 1.602*10**-19 #charge of an electron(C)
Eo = 8.85*10**-12 #permittivity of free space(C/N -m)

#Calculations
Ce = (A*(e**2)*(1-(1/n)))/(4*pi*Eo*ro) #joules
Ce_ev = Ce/e                           #Converting joules to eV

#Result
print "The cohesive energy of NaCl molecule is",round(Ce_ev,2),"eV"

The cohesive energy of NaCl molecule is 7.97 eV