This document discusses radioactive decay and types of radiation. It explains that some isotopes are unstable and radioactive, meaning they will decay over time by emitting radiation. There are three main types of radiation: alpha, beta, and gamma. Alpha radiation involves emitting a helium nucleus, beta involves emitting an electron, and gamma involves emitting high-energy electromagnetic radiation. The document provides examples of alpha, beta, and gamma decay and discusses the penetrating power and shielding of each type. It also notes some uses of radiation such as tracking movement in organisms and determining the age of ancient objects.

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
U235
92
alpha
Th231
90

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
C14
6
e-
N14
7

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.