1. Radioactivity
Chapter 4: Section 1

2. Discovering Radioactivity
Henri Becquerel hypothesized that fluorescent minerals give off X rays

3. Unexpected Result
Review Page 88 to answer the following question in your notes:
How did Becquerel discover that energy comes from Uranium, an element in the mineral?

4. Naming the unexpected
Nuclear Radiation: high energy particles and rays that are emitted by the nuclei
Radioactivity: the process by which an unstable nucleus gives off nuclear radiation

5. Kinds of Radioactivity

6. Alpha Decay
Alpha () – an atom decays into a new atom and emits an alpha particle
2 protons and 2 neutrons – the nucleus of a helium atom
Mass= 4 Charge= + 2
Alpha particle
Unstable nucleus
New nucleus

7. Alpha Decay
Example: Radium-226

8. Conservation of Decay Look at example on page 89
Mass number is conserved.
Charge is conserved

9. Beta Decay
Beta () – an atom decays into a new atom by changing a neutron into a positron or a electron.
Charge= -1 or +1
Mass= 0
Beta particle
Unstable nucleus

10. Two Types of Beta Decay
Carbon 14

11. Two Types of Beta Decay O 8 18 O 8 16 O 8 17
An isotope is an atom with a different number of neutrons:
Notice that the mass number is different. How many neutrons does each isotope have? O 8 18 O 8 16 O 8 17
Each isotope has 8 protons – if it didn’t then it just wouldn’t be oxygen any more.

12. Gamma Decay
Gamma – after  or  decay surplus energy is sometimes emitted.
Occurs when particles of a nucleus shift
The atom is not changed. No mass or charge
Unstable nucleus
New nucleus
Gamma radiation

13. Penetrating Power of Radiation

14. Damage to Matter
When an organism absorbs radiation, its cells can be damaged
Radiation sickness
Fatigue and Loss of appetite
Hair loss
Death
Cancer
Radiation can also damage non-living matter

15. Uses of Radioactivity
Isotopes are used to determine the age of objects
Smoke detectors
Tracers: radioactive elements whose paths cane be followed through a process or reaction

16. Radioactivity in real life
Doctors use tracers to help diagnose problems
They have short half-lives and are fed or injected into patient
Follow it as it travels through the body
Isotopes can detect defects in structures
Radiation is used to detect thickness in metals

17. Radiation Survey
Annual Radiation Survey