Do Now (5/1/14):
• Pick up a note sheet from the back on your
way in
• What particles exist in an atom? (on a new Do
Now sheet)
• Rank those particles in order of most massive
to least massive (if you are not sure, guess)
Mass Defect, Binding Energy, and
Nuclear Reactions
5/1/14
Mass Defect:
• The difference between the sum of the mass of the
individual nucleon (proton or neutron) and the actual mass.
m  matom


Z m  m 
p
e

 


(A

Z)m

n 
Example:
• Find the mass defect of a copper-63 nucleus if
the actual mass of a copper-63 nucleus is
62.91367 amu
Find the composition of the copper-63 nucleus and determine the combined mass of its
components.
Copper has 29 protons and copper-63 also has (63 - 29) 34 neutrons.
The mass of a proton is 1.00728 amu and a neutron is 1.00867 amu.
The combined mass is calculated:
29 protons(1.00728 amu/proton) + 34 neutrons(1.00867 amu/neutron)
or
63.50590 amu
Example:
• Find the mass defect of a copper-63 nucleus if
the actual mass of a copper-63 nucleus is
62.91367 amu
• Calculate the mass defect.
• Dm = 63.50590 amu - 62.91367 amu
= 0.59223 amu
Binding Energy
E binding 
(m assdefect(inu))(931.49MeV /u)
• The energy equivalent of the mass defect; it is
always negative
 It
is the minimum amount of energy needed to break
the nucleus into its component nucleons.
Binding Energy of Alpha Particle
For the alpha particle Δm= 0.0304 u which
gives a binding energy of 28.3 MeV
It Takes a Lot More Energy to Split a Nucleus
Than to Ionize an Atom
Practice:
Work on the Mass Defect
worksheet.
Finish all mass defect and binding
energy problems by the end of
class for extra credit!
Do Now (5/2/14):
1. What is the mass defect of an alpha particle
if its mass is 4.00153u?
2. What is the binding energy of an alpha
particle?
Nuclear Notation
Balancing Nuclear Decay Equations
92U
238
--------> 90Th234 + 2He4
Subscripts are "proton
numbers"
Superscripts are "nucleon
numbers"
Proton and nucleon counts
must be the same:
92 = 90 + 2
238 = 234 + 4
Decay Sequence
Alpha decay sequence:
235
4
U
92
231
He +
2
209
4
Po
84
Th
90
205
He +
2
Pb
82
Decay Sequence
Beta decay sequence:
14
14
C
6
e
N +
7
228
Ra
88
0
-1
228
0
e
Ac +
89
-1
Practice:
• Use the rest of class to work on “Mass Defect
and Binding Energy” and “Nuclear Reactions.”