1. Nuclear Chemistry Chapter 25 You should be able to describe types of decay and their strength.

2. Radiation: Energy or particles emitted by radioactive source and travel through a medium or space. FDA recommends < 500 millirems per year  Dental xrays = 20 mrem  Smoke detectors 2 mrem/yr

3. Another reason to not smoke: 2 packs a day = 10,000 mrems a year!

4. Radiotracers: medically important!

5. Radioactivity = Instability

6. Radioisotopes Only 17% of all known isotopes are stable and do not decay spontaneously. Band of stability

7. Types of Radiation The three most common types of radiation are alpha (α), beta (β), and gamma (γ).

8. Types of Decay: Alpha Decay: Nucleus is too heavy (>83 protons) and releases 2 protons & 2 neutrons Symbolized by greek letter alpha = α Weakest form of decay, can be stopped by sheet of paper.

9. Beta Decay Nucleus releases an electron? Neutron = proton + electron Unstable because it has too many neutrons vs. protons (band of stability) Symbolized by greek letter beta β Can be stopped by metal foil

10. Positron Emission A positron is a particle with the same mass as an electron but opposite charge, thus it is represented by the symbol.

11. Electron Capture Electron capture is the other common radioactive decay process that decreases the number of protons in unstable nuclei lying below the band of stability.

12. Positron emission and electron capture After an unstable atom undergoes electron capture or positron emission, the resulting atom is closer to, if not within, the band of stability. Click box to view movie clip.

13. Gamma Radiation. Gamma rays are high-energy (short wavelength) electromagnetic radiation. They are denoted by the symbol. Symbolized by greek letter, gamma Several cm of lead are needed to stop

14. Isotopic Notation Atomic # = protons (from periodic table) Mass # = protons + neutrons Cobalt-60

15. Decay and particles Alpha Beta Gamma Proton Neutron electron 4 2 He 0 -1 e 0 0 γ 1 1 p + 1 0 n o 0 -1 e