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 or 00y).
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 (α emission)

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

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