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63 terms

Radioactivity

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Radioactivity
the spontaneous emission of a stream of particles or electromagnetic rays in nuclear decay
Radiation
energy that is radiated or transmitted in the form of rays or waves or particles
Radioisotope
Isotope with an unstable nucleus that becomes more stable by spontaneously emitting energy and particles.
Transmutation
(physics) the change of one chemical element into another (as by nuclear decay or radioactive bombardment)
Alpha Particle
A type of nuclear radiation consisting of two protons and two neutrons
- Symbol: a or He
- Notation: 4/2a (or 4/2 He)
- Mass: 4 amu
- Charge: 4+
-Penetrating power: Low (Paper)
Beta Particle
An electron emitted from the nucleus during some kinds of radioactive decay
- Symbol: B-
- Notation: 0/1B
- Mass: 0 amu
- Charge: -1
-Penetrating Power: Moderate (Metal Foil)
Positron
A particle with the mass of an electron but a positive charge
- Symbol: B+
- Notation: 0/1 B+ or 0/1 e
- Mass: 0
- Charge: +1
- Penetrating Power: Moderate (Metal Foil)
Gamma Radiation
Electromagnetic waves with the shortest wavelengths and highest frequencies, electromagnetic radiation emitted during radioactive decay and having an extremely short wavelength
- Symbol: Y
- Notation: 0/0 Y
- Mass: 0 amu
- Charge: 0
- Penetrating Power: High (Lead and Concrete)
Ionizing Radiation
enough energy to knock electrons from atoms forming ions, capable of causing cancer (gamma-X-rays-UV)
Isotopes
Atoms of the same element that have different numbers of neutrons and therefore different mass numbers
Stability of an Isotope
Is based on the ratio of the neutrons to protons in its nucleus
How Nuclei of Unstable an isotope gain stability
(Spontaneous Decay) : Trying to correct the Neutron to Proton Ratio
Band (Belt) of stability
A Graph that shows the number of neutrons to the number of protons; stable nuclei are found in the shaded area
Stable Isotopes
Only exist at or before the atomic number 83
4 Types of Radioactive Decay
Alpha, Beta, Positron, Gama
Electrons
Travel towards positives
Positive Charge and Weak Penetrating Power
Alpha
Order of Increasing Mass of Particles
electron --> proton --> alpha particle
Similar to high energy X-Rays
Gamma
Neutrons
Mass but no charge
Alpha Decay
An atoms which emits an alpha particle (a helium nucleus) is called an alpha emitter
- atomic number of daughter nucleus will be decreased by 2 and the mass number will be decreased by 4
Beta Emitter
An atom which emits a beta particle
Positron Emission
Proton Changes to a neutron
Half-Life
Time required for half of a given sample of a radioisotope to decay
What affects Radioactive Substances
NOTHING: Radioactive substances decay at a constant rate an CANNOT be altered by factors such as temperature, pressure, or chemical combination
-->
Acts as 1 Half life
30 --> 15 --> 7.5
2 halve Lives
What happens during a half life
(16mg --> 8 mg --> 4 mg --> 2 mg) After 3 halve lives the other 14 grams was transformed into other substances
How much of a 100g sample of 198 Au is left after 8.10 days if its half-life is 2.70 days?
12.5
The half of 42K is 12.4 hours. How much of 750 g sample is left after 62 hours?
23.4375
What is the half-life of 99Tc if a 500g sample decays to 62.5 g in 639,000 years?
213,000
The half-life of 232Th is 1.4 x 10^10 years. If there are 25.0 g of the sample left after 2.8 x 10^10 years, how many grams were in the original sample?
100g
A 50 g sample of 16N decays to 12.5 g in 14.4 seconds. What is the half-life?
7.2
There are 5.0 g of 131I left after 40.35 days. How many grams were in the original sample if its half-life is 8.07 days
150g
Tracers
Because radioisotopes chemically resemble the stable isotopes of the same element they can be used as tracers to follow the course of a reaction
Radioactive isotopes used for diagnostic purposes
Should have SHORT half-lives and be QUICKLY eliminated from the body
I-131
Thyroid Disorders
Technetium-99
Pinpoint Brain tumors
Co-60
Treating Cancer
C-14 to C-12 ratio
Date formerly living organisms
Example of Carbon (14-12) Dating
When a tree takes in CO2, it takes in C-14 and C-12. When the ratio of C-14 to C-12 is the same ratio as in the atmosphere. But when the tree dies the C-14 decays and is not replaced and thereby changing the ratio over time
U-238 to Pb-206 ratio
Dates geological formations, such as the age of mineral
What is the nuclear decay mode for the change from Pb-214 to Bi-214
Beta Decay
Industrial Measurements
Radioactive isotopes can measure the thickness of many industrial products
Kill Bacteria
Radiation allows food to be stored longer by eliminating bacteria, yeast, molds, and insects from food
Induced Artificial Transmutation
Artificial transmutation can be induced by the BOMBARDMENT of the nucleus by high-energy particles
Particle Accelerators
Cyclotron or synchrotron
Use electric and magnetic fields to provide charged particles, such as an alpha particle with sufficient kinetic energy to overcome electrostatic forces and penetrate a target nucleus
Second way of Artificial Transmutation
Occurs when a neutron collides with a target nucleus. The neutrons can be obtained as by-products of nuclear reactors, since the neutron doesn't have a charge, it is not repelled by the target nucleus.
Nuclear Reactions vs. Chemical Reactions
The energy released during nuclear reactions is far greater than the energy given off from chemical reactions
Products vs. Reactants of a Nuclear Reaction
Products have less mass than the reactants
Mass defect
The error between the recants and the products has been converted into energy
Nuclear Fission and Nuclear Fusion
Reactions utilizing sources of energy
Nuclear Fission
The SPLITTING of a nucleus into smaller fragments, accompanied by the release of neutrons and a large amount of energy
- Results from Neutron Capture
- Result is unstable
Fission Reaction
Must be PU-239, U-235, or U-233!
- Has one nuclear isotope combine with a neutron to form two real isotopes, a neutron, and energy
- The reaction is controlled and able to produce useful energy
Atomic Bomb
Chain Reaction is NOT controlled
Problems with Fission Reactors
- Radioactive waste
- Storage is difficult to find
- Time Consuming and costly
- Health hazards
Nuclear Fusion
Process of combining light nuclei to produce a nucleus of greater mass
- process that the sun uses to produce energy
- HYDROGEN NUCLEI REACT TO PRODUCE HELIUM
What is needed for a Fusion Reaction
- Extremely High temperatures
Thermonuclear Device
An explosive device based on a nuclear fusion reaction
Nuclear Bomb
Utilizes fission as a trigger for Fusion
Fusion vs. Fission
- Nuclear fusion releases more energy than nuclear fission for a given mass of fuel
- Nuclear fusion power plants would produce little radioactive waste (unlike fission)
- Potential fuels readily available
Are there currently any successful fusion reactors
No
What are some problems scientists are still facing?
High temperatures requirements and containment forces