Belt of Stability

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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

+

1

0

e

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

+

1

0

e

120

53

I

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

+

2

4

He

1

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 238 U and end with 206 Pb

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

2

Binding Energy per Nucleon

Elements with intermediate masses have the highest nuclear binding energies

Chain Reaction

3

Nuclear Weapons

Nuclear Reactor

Nuclear Power Plant

4

Nuclear Fusion

5

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