1. Radioactive Elements
Chapter 4.5

2. Review: Radioactive decay
 the atomic nuclei of unstable isotopes
release fast-moving particles and energy

3. alpha particles beta particles gamma rays
3major forms of radiation produced during the radioactive decay of an unstable nucleus. 
alpha particles
beta particles
gamma rays

4. Alpha Decay
two protons and two neutrons  break off from the nucleus (alpha particle)
2 p+ and 2 n
(He)

5. Beta Decay
a neutron inside the nucleus changes into an electron and a proton
The fast moving electron (beta particle) leaves
The proton stays in the nucleus
Overall the mass stays the same (one neutron turned into one proton, each weight 1 amu)
a different element is formed (e.g. Carbon-14 becomes Nitrogen-14)

6. Gamma Radiation/Gamma Rays (ENERGY)
Almost always produced with alpha and beta decay
high-energy waves
has no charge and does not cause a change in either the atomic mass or the atomic number.

7. Penetration of Radiation Particles
Though very small and very fast moving, radiation particles can be stopped when they collide with other atoms
Alpha particles are least penetrating – can be stopped by paper
Gamma particles are most penetrating, need several cm of lead or ~1 m of concrete to stop them

8. Types of Radiation Produced by Radioactive Decay
Gives Off
New Nucleus
Characteristics
Alpha Decay
2 protons and 2 neutrons  (Alpha Particle)
Positive charge
New element – 2 less protons, 2 less neutrons
Weighs 4 amu less
Fast; Blocked by paper
Can damage skin
Beta Decay
One fast moving electron (Beta Particle)
Negative charge
New element – 1 less neutron, 1 more proton
Weighs the same
Faster/More penetrating; Pass through paper, blocked by aluminum sheet
Can travel into human body
Gamma Radiation
High Energy Waves
Given off with alpha and beta decay
no charge
No change to atomic mass or number
Most penetrating; Need thick lead or ~1 meter of concrete to stop
Can pass right through a body

9. Some Uses of Radiation
A radioactive isotope “signals” where it is by emitting radiation that can be detected.
 Tracers are radioactive isotopes that can be followed through the steps of a chemical reaction or industrial process. 
Used by biologists to learn about plants
Used to find weaknesses in metals, such as pipes and cracks in structures
Used in medicine to diagnose problems and treat cancer

10. What do I need to know about radioactivity for the test?
Henry Becquerel discovered Radioactive decay
Radioactive decay – unstable nucleus releases:
fast moving particles (alpha and beta particles)
and energy (gamma radiation)
3. Alpha rays can be blocked by paper. Beta Rays blocked by an aluminum sheet.
4. Tracers – are radioactive isotopes that can be used by doctors to detect medical problems