Understanding Nuclear Radiation and Radioactivity

1. Nuclear Radiation

2. Radioactivity • Radioactivity – The spontaneous release of energy by a nucleus. • Radiation – the penetrating rays and particles emitted by a radioactive source. • Radioisotopes – the nuclei of unstable isotopes. • The difference between chemical reactions and nuclear reactions are that in a nuclear reaction radioisotopes gain stability by undergoing changes and temperature, pressure and/or the presence of a catalyst do not affect these reactions.

3. Radioactivity (Continued) • Too many or too few neutrons relative to the number of protons makes a nucleus unstable. • An unstable nucleus releases energy by emitting radiation during the process of radioactive decay. Are atoms really indivisible as Dalton said? No, radioactivity disproved Dalton’s assumption.

4. Types of Radiation • The three main types of radiation are alpha radiation ( α or 42He), beta radiation (β- or 0-1e) and gamma radiation (γ or00y). • Alpha particle – contains two protons and two neutrons and has a double positive charge. • Low penetrating power. • Shielding: paper – clothing (dangerous if ingested.) Example of alpha decay (transformation) 23892U --------> 23490Th + 42He (αemission)

5. Types of Radiation (Continued) • Beta particle – high velocity electrons • Moderate penetrating power. • Shielding: Metal foil Example of beta decay 146C -----> 147N + 0-1e (βemission)

6. Types of Radiation (Continued) • Gamma Ray – A high energy photons emitted by radioisotopes. • High penetrating power. • Incompletely shields (Lead, concrete) • Nuclei often emit gamma rays along with alpha and beta particles during radioactive decay. Example of gamma emission. 23090Th --------> 22688Ra + 42He + γ

7. 25.1 Section Assessment pg. 802 #’s 3-6 Read Section 25.2 pgs. 803-808