1. Radioactivity
Henri Becquerel discovered X-rays in As a result of his experiments, he also discovered other forms of rays that could be emitted that had not previously been detected. If you are interested in his research, read pages 266 – 267 in your textbook.

2. The Nature of Nuclear Radiation
Nuclear Radiation cannot be seen, but they have certain characteristics
Radiation alters photographic film
Radiation produces fluorescence
Electric charge can be detected
Radiation damages cells in most organisms

3. Radioactivity is the release of nuclear radiation in the form of particles and rays from a radioactive element.
Types of Radiation
Alpha particles
Beta particles
Gamma rays

4. Turn to your partner and list the 3 types of radiation.
Brain Break
Turn to your partner and list the 3 types of radiation.

5. Alpha Particles Nucleus of a helium atom with 2 protons and 2 neutrons
Has a positive charge because it has no electrons
Weakest form of nuclear radiation
Alpha particles can burn skin
Alpha particles can be stopped by a piece of paper
Uses the symbol α

6. Beta Particles
Beta particles are an electron that is formed inside the nucleus when a neutron breaks apart
Can penetrate 100 times greater than alpha particles
Can pass through 3 mm of aluminum
Uses the symbol β

7. Gamma Rays
Gamma Rays
Gamma rays are electromagnetic waves of extremely high frequency and short wavelength
Gamma rays carry much more energy than visible light
Most penetrating radiation given off by radioactive elements
Can pass through several centimeters of lead
Uses the symbol ɣ

8. Brain Break
Gamma Rays
Tell your partner one thing about alpha particles, beta particles, and gamma rays.

9. Gamma Rays Nuclear Stability
Nuclear strong force holds protons and neutrons together in the nucleus.
The energy associated with this is called binding energy.
This energy is essential to the stability of an atom.
Some elements do not have stable nuclei. The unstable nucleus will come apart. These elements are referred to as radioactive.

10. Gamma Rays Nuclear Stability Alpha decay Beda decay Gamma decay
An unstable nucleus can become stable by undergoing a nuclear reaction or change.
There are 3 types of radioactive decay.
Alpha decay
Beda decay
Gamma decay

11. Alpha Decay
Gamma Rays
Occurs when a nucleus releases an alpha particle (2 protons and 2 neutrons)
This decreases the mass by 4 but the number of protons is only reduced by 2. Because of this, the original element is no longer the same.
Example: Uranium 238 undergoes alpha decay. The 238 represents the mass. The atomic number of uranium is 92. When it undergoes alpha decay, it becomes thorium (Th) which is the element with the atomic number 90 since uranium lost 2 protons.

12. Beta Decay
Gamma Rays
A beta particle is an electron formed inside the nucleus when a neutron breaks apart. A proton also is produced when a neutron breaks apart.
Beta decay occurs when a beta particle is released from a nucleus.
When beta decay occurs an element with a mass number one higher is formed because during beta decay, the element gains a proton.
The process in which one element is changed into another as a result of changes in the nucleus is called transmutation.

13. Gamma Decay
Gamma Rays
When a gamma ray is emitted by a nucleus, the nucleus does not change into a different nucleus.
A gamma ray is an extremely high-energy wave.
In gamma decay, the nucleus makes a transition to a lower energy state.

14. Brain Break
Gamma Rays
When radium-226 undergoes alpha decay, what does it become?
When radium-226 undergoes beta decay, what does it become?

15. Radioactive Half-Life
Gamma Rays
Half-life is the fixed rate of decay of a radioactive element.
Carbon-14 has a half-life of 5,730 years. If I had a 22 g sample of carbon-14, I would only have 11 g left after 5,730 years. I would then after 11,460 years, I would only have 5.5 g left.
Barium-139 has a half-life of 86 minutes. If I had 20 g of barium-139, after 86 minutes, I would only have 10 g left. After 172 minutes, I would only have 5 g left. After 258 minutes, I would only have 2.5 g left.

16. Gamma Rays Nuclear Fission
Nuclear fission is the splitting of an atomic nucleus into two smaller nuclei of almost equal mass.
Fission does not occur spontaneously like radioactive decay.
When an atom undergoes fission, the amount of energy released from one atom is not that great. The neutrons released, however, are capable of splitting other atoms. This creates a nuclear chain reaction in which billions of fission reactions can occur each second. This produces huge amounts of energy.
Nuclear power plants use controlled fission reactions to produce energy.

17. Gamma Rays Nuclear Fusion
Nuclear fusion is the joining of two atomic nuclei of smaller masses to form a single nucleus of larger mass.
For fusion to occur, the temperature must be well over a million degrees Celsius. At temperatures this hot, plasma is formed. Plasma consists of positively charged ions, which are the nuclei of original atoms, and free electrons.
The energy released in fusion reactions is far greater than that released in fission reactions. Fusion reactions produce less radioactive waste, and possible fuels for fusion are more plentiful.
Fusion reactions are more difficult to begin, to control, and to maintain than fission reactions.

18. Brain Break Gamma Rays Define fusion
Define fission
Define fusion
Calculating half life: The half-life of Pa-234 is 6.75 hours. How much of a 12.5 g sample remains after hours?

19. Instruments to Detect Radioactivity
Gamma Rays
Electroscope
Geiger counter
Cloud chamber
Bubble chamber

20. Radioactivity in our Lives
Gamma Rays
Carbon dating of organic materials
Finding leaks or weak spots in metal pipes
Medical testing
MRI scans
Used to destroy unhealthy cells that cause cancer
Killing bacteria that cause food to spoil

21. Dangers of Radiation Gamma Rays
The same radiation used to treat diseases can also cause diseases.
Damage to biological tissue—especially DNA
Reddening of the skin and a drop in white blood cell count, nausea, fatigue, and loss of hair.
Exposure can be fatal—this was the cause of Marie Curie’s death in 1934.
Metal structures can be weakened.