The Stability of Nuclides

1. The Stability of Nuclides

2. For elements with a small atomic number we find that they tend to be stable when Z≈N :for example N Z

3. For nuclides with larger mass the line of stability moves from the N=Z line. More neutrons are needed This is because of the repulsive electromagnetic force acts over a longer range that the strong force and as the nuclear diameter increases the electromagnetic repulsions must be “diluted” by the presence of extra neutrons. Stable nuclides The Segre Chart

4. No stable nuclides exist above proton number = 83 If a nuclide has a higher proton number it will decay generally by alpha emission. In this way it decreases in Z and N and approaches the line of stability. There are many chains involving successive alpha decays. Eventual products are stable isotopes Stable nuclides α decay region The Segre Chart

5. region of stability

6. BETA DECAY Beta (-) decays take neutrons to protons region of stability

7. β- emitters therefore lie above the stability region β- emitters

8. Positron emission Is the opposite of beta emission in which a proton is converted to a neutron region of stability

9. β+ emitters lie below the stability line.. In electron capture (K capture) electrons are drawn into the nucleus and combine with protons. The effect of this is to convert a neutron to a proton. β+ emitters

10. In electron capture (K capture) electrons are drawn into the nucleus and combine with protons. A proton is converted to a neutron region of stability

11. Electron Capture electron capture occurs with elements below region of stability