for cambridge edexcel syllabus

1. Chapter 31
Nuclear Physics and
Radioactivity

2. 31.1 Nuclear Structure
The atomic nucleus consists
of positively charged protons
and neutral neutrons.

3. 31.1 Nuclear Structure















neutrons
of
Number
protons
of
Number
neutrons
and
protons
of
Number
N
Z
A 

atomic
number
atomic mass
number

4. 31.1 Nuclear Structure
Nuclei that contain the same number of protons but a different
number of neutrons are known as isotopes.

5. 31.1 Nuclear Structure
  3
1
15
m
10
2
.
1 A
r 



6. 31.2 The Strong Nuclear Force and the Stability of the Nucleus
The mutual repulsion of the protons
tends to push the nucleus apart. What
then, holds the nucleus together?
The strong nuclear force.

7. 31.2 The Strong Nuclear Force and the Stability of the Nucleus
As nuclei get larger, more
neutrons are required for
stability.
The neutrons act like glue
without adding more repulsive
force.

8. 31.3 The Mass Deficit of the Nucleus and Nuclear Binding Energy
    2
2
deficit
Mass
energy
Binding c
m
c 



9. 31.3 The Mass Deficit of the Nucleus and Nuclear Binding Energy
Example 3 The Binding Energy of the Helium Nucleus Revisited
The atomic mass of helium is 4.0026u and the atomic mass of hydrogen
is 1.0078u. Using atomic mass units, instead of kilograms, obtain the
binding energy of the helium nucleus.

10. 31.3 The Mass Deficit of the Nucleus and Nuclear Binding Energy
u
0304
.
0
u
0026
.
4
u
0330
.
4 


m
MeV
5
.
931
u
1 
MeV
3
.
28
energy
Binding 

11. 31.3 The Mass Deficit of the Nucleus and Nuclear Binding Energy

12. 31.4 Radioactivity
A magnetic field separates three types of particles emitted by
radioactive nuclei.

13. 31.4 Radioactivity
α DECAY
He
D
P 2
2
4
2 
 

A
Z
A
Z

14. 31.4 Radioactivity
A smoke
detector

15. 31.4 Radioactivity
β DECAY
e
D
P 0
1
1 
 
 A
Z
A
Z

16. 31.4 Radioactivity
γ DECAY

P
P 

 A
Z
A
Z
excited energy
state
lower energy
state