Belt of Stability
Nuclei above the belt of
stability have too many
neutrons (per proton)
They tend to decay by
β-emission, which
decreases the n/p+ ratio
Example
120
49
In →
120
50
Sn + -10e
Belt of Stability
Nuclei below the belt of
stability don’t have enough
neutrons (per proton)
They tend to decay either by
electron capture (for heavy
elements) or positron
emission (for light elements),
both of these processes
increase the n/p+ ratio
118
54
Xe + -10e →
120
53
I
1
Belt of Stability
Nuclei with atomic
numbers greater than
83 are all unstable.
They have too many
protons and neutrons.
They tend to decay by
α-emission
239
94
Pu →
237
92
U + 42 He
Radioactive Series
Large radioactive nuclei
cannot stabilize by
undergoing only one
nuclear transformation.
They undergo a series of
decays until they form a
stable nuclide (often a
nuclide of lead).
This example shows a series
of α- and β-decays that start
with 238U and end with 206Pb
2
Other Considerations
Nuclei with 2, 8, 20, 28, 50, or 82 protons or 2, 8, 20, 28,
50, 82, or 126 neutrons tend to be more stable than
nuclides with a different number of nucleons.
Radioactive Decay – Half Life
3
Binding Energy per Nucleon
Elements with intermediate masses have the highest nuclear binding energies
Chain Reaction
4
Nuclear Weapons
5
Nuclear Reactor
Nuclear Power Plant
6
Nuclear Fusion
7