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 Z N

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. The Segre Chart Stable nuclides

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 The Segre Chart Stable nuclides α decay region

5. region of stability

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

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

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

9. β + emitters lie below the stability line.. β + emitters 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.

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

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