1. Mass of constituent parts of the nucleus:
4He is the most abundant isotope of helium. Its nuclear mass is x 10-27kg. What is: a) The mass defect? b) The binding energy of the nucleus in joules? c) The binding energy of the nucleus in electron volts?
He has 2 protons
4He has 2 neutrons
Mass of constituent parts of the nucleus:
2 ( x ) + 2 ( x 10-27) = x kg
mass defect = x x 10-27
x kg
x J
E = mc2
E = ( x 10-29)(3 x 108)2
28.41 MeV

2. Find the binding energy of Xe-131 (atomic mass of 131.2907 u)
Xe has 54 protons
5.68 MeV per nucleon
131Xe has 77 neutrons
Mass of constituent parts of the nucleus:
54 ( ) + 77 ( ) = u
Actual mass of the nucleus =
– 54( ) = u
Mass defect =
= u
Binding energy = ( )(931) =
744MeV

3. Calculate the energy balance of the following
Mev
mass on right side
mass on left side u u u u
Mass difference =
= u
Energy Balance = ( )(931) =
4.80 MeV

4. mass on right side mass on left side 4.001500 u 238.0508 u
238U decays into 234Th and an alpha particle
a) Write the decay equation
b) How much energy is released?
Mass of U = u
Mass of Th -234 = u a)
mass on right side b)
mass on left side u u u u
Mass difference =
= u
Energy Balance = (0.0067)(931) =
6.24 MeV