1. Radioactive Decay

2. Radioactive Decay
Yesterday we learned that all elements have different isotopes.
Example:
1H (1 proton, 0 neutrons)
2H (1 proton, 1 neutron)
3H (1 proton, 2 neutrons)
Some isotopes are stable and will last essentially forever.
Some aren’t stable.

3. Radioactive Decay An unstable isotope is said to be radioactive.
Radioactive (unstable) isotopes = radioisotopes
Radioisotopes eventually decay into more stable forms.
A radioisotope releases energy by emitting radiation during the process of radioactive decay.

4. Radioactive Decay
Carbon-12 and carbon-13 are stable, but carbon-14 is radioactive.
6 p+ and 6 n0
6 p+ and 7 n0
6 p+ and 8 n0

5. What makes a radioisotope unstable?
An isotope can be unstable if:
it is too heavy (more than 83 protons).
its n0 to p+ ratio is too high.
its n0 to p+ ratio is too low.

6. Types of Radiation Alpha radiation
Composition: Alpha particle (helium nucleus)
Symbol:  or 4He
Charge: +2
Mass: 4 amu
Penetrating power: Low (0.05 mm body tissue)
Shielding: Paper, clothing
Effect on nucleus: Z – 2, A – 4

7. Alpha Decay
alpha

8. Types of Radiation Beta radiation
Composition: Beta particle (electron)
Symbol:  or e-
Charge: -1
Mass: 1/1837 amu
Penetrating Power: Moderate (4 mm body tissue)
Shielding: Metal foil
Effect on nucleus: Z + 1; A unchanged.

9. Beta Decay e-

10. Types of Radiation Gamma radiation
Composition: High-energy EM radiation
Symbol: 
Charge: 0
Mass: 0
Penetrating power: Very high
Shielding: Lead, concrete
Effect on nucleus: decreases energy

12. Uses of Radiation
Radioisotopic labelling – can be used to track the movement of a particular substance through a living organism.
Radiometric dating – used to determine the age of ancient objects.
Many uses in medicine, from imaging to cancer therapy.