Physical Science Mr. Willis

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

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

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

3 Types of Radioactive Particles produced during decay:

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

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

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

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

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

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

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

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

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

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

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, 1945. The bomb dropped was called little boy and had a yield of 15 kilotons. The mushroom cloud rose to over 60,000 feet.

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.

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

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.

15 Megatons

Operation Castle -Marshall Islands, 1954 -15 Megatons