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

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