8-9 / 3107
Line of stability
Too many
neutrons
for stability
Stability: equilibrium of forces
Radioactivity
•
H. Becquerel discovered radioactivity in 1896
•
A property of nuclei
•
Due to inherent physical properties, a
nucleus may be not stable and likely to
undergo a nuclear transformation.
Long ranged
Electrostatic forces
p
b
-
decay
n=>p
+
+e
-
+
n
H-3, C-14, I-131
Too many
protons
for stability
•
This process can be fast (short half life) or
slow (long half life).
•
The time of transformation cannot be
predicted for an individual nucleus - it is a
random event which can only be adequately
described using statistics
Short ranged
Nuclear forces
p
n
b
+
decay
p
+
=>n+ e
+
+
n
O-16, F-18
electron capture
p
+
+ e
-
=>n+
n
Xe-125
→
I-125, Tl-201