1. Physical Science Mr. Willis

2. Radioactivity…
is the spontaneous disintegration, or decay, of the nuclei of certain elements to produce other elements
during nuclear decay, various types of energy and particles are released from the nucleus, changing the atoms of an element into a completely different element
An unstable isotope is called a radioisotope

3. Henri Becquerel
Won Nobel Prize in 1903 along with Curies(next slide) for discovery of spontaneous radioactivity

4. Pierre & Marie Curie (on right)
Marie would go on to win another Nobel Prize in 1911 for discovering Radium & Polonium.
She would later die, however, from overexposure to radiation

5. 3 Types of Radioactive Particles produced during decay:

6. Alpha(α) Decay…
Release of alpha particle, which is a helium nucleus with 2p+ & 2no & a positive charge
Result of α decay is to decrease the atomic # of a radioactive nucleus by 2 and its’ mass number by 4.
Ex. #84 Polonium-212 would decay to #82 Lead-208
A single sheet of paper is all that is needed to block α particles

7. Beta(β) decay
Release of Beta particle, which is a high-speed electron with a negative charge
Result of β decay is to increase atomic # by 1 & leave mass # unchanged
Ex. #43 Technetium-98 would decay to #44 Rubidium-98
β particles have more penetrating power, but can be stopped by a thin sheet of aluminum

8. Gamma(γ) decay
Release of strong electromagnetic waves which have a short wavelength and high frequency, but no charge
Very dangerous. It takes several centimeters of lead to stop them.
α, β, & γ rays can be separated using a magnetic field since they have different charges

11. Half-Life…
is the time required for ½ of the original radioactive substance to decay.
can vary from seconds to years depending on the element
Important when dealing with radioactive nuclear waste because waste will stay dangerous for thousands of years as it decays to a stable form

12. Fission Fission is the splitting of a nucleus into fragments
The combined mass of the fragments is a little less than the original mass because some of it is converted into energy using Einstein’s equation E=mc2
Fission Reaction
Chain Reaction video

13. Nuclear Power Uses fission to split atoms & release energy
Reaction rate controlled by control rods, which absorb neutrons
Uranium is most common fuel and produces radioactive krypton & barium

14. Fusion
Fusion is when the nuclei of atoms are fused together, releasing even more energy than fission
Only occurs at extreme temperatures, such as is found in the sun
In the sun, 4 H nuclei combine to form 1 He nucleus, 2 e- and energy
Fusion is 16 million times more powerful than combustion
Governments are currently working on building a fusion reactor, which would eliminate energy problems and produce no harmful waste
Fusion Reaction

16. Atomic Bombs
1st 2 atomic bombs dropped were little boy & fat man

17. A fission bomb is the result of an uncontrolled fission reaction in which the released neutrons spontaneously support continued reactions, releasing a huge amount of energy

18. A fusion bomb is much more powerful, but requires the heat & energy produced by a fission bomb to detonate it

19. The mushroom cloud rising over Hiroshima, Japan
The mushroom cloud rising over Hiroshima, Japan. The city of Hiroshima was the target of the world’s first atomic bomb attack at 8:16 a.m. on August 6, The bomb dropped was called little boy and had a yield of 15 kilotons. The mushroom cloud rose to over 60,000 feet.

22. The Red Cross building was very close to the hypocenter
The Red Cross building was very close to the hypocenter. Note the depressed roof caused by the explosion occurring overhead.

23. View of the bank district, east from Shima Hospital, the hypocenter.

24. The foreground shows the ruins of the Hiroshima Gas Company Building (800 feet from the hypocenter). In the center are the ruins of the Honkawa Elementary School.

25. 15 Megatons

27. Operation Castle -Marshall Islands, 1954 -15 Megatons