2A3 Nuclear Processes Flashcards
Explain the characteristics and effects of nuclear processes such as radioactive decay, fission, and fusion. (45 cards)
Define:
Radioactivity
The spontaneous emission of energy or particles (such as alpha particles, beta particles, or gamma rays) from unstable atomic nuclei in an attempt to become more stable.
This process, known as decay, allows the nucleus to become more stable.
Define:
Decay series
A sequence of radioactive decays a nucleus undergoes to become stable.
For example, Uranium-238 decays through a series of reactions to form stable Lead-206.
When is a nucleus considered unstable?
When nuclear forces cannot overcome electrostatic repulsive forces between protons.
An unstable nucleus undergoes a change that releases energy in the form of a particle or ionizing radiation.
Stability depends on the ratio of neutrons to protons (n/p).
Fill in the blanks:
Nuclear reactions conserve both _______ and _______ during any reaction or decay process.
nucleon number; charge
During a nuclear reaction or decay, the nucleon number (total protons and neutrons) and the net charge are always conserved, ensuring no loss or gain in mass or charge.
What are the three main types of nuclear processes?
- Radioactive decay
- Fission
- Fusion
These processes release energy by altering atomic nuclei.
Define:
half-life
The time it takes for an initial amount of radioactive material to reduce to half its original amount.
The half-life is a constant property for a given radioactive isotope but varies between different elements and isotopes.
Some isotopes have half-lives of fractions of a second, while others (like Uranium-238) can have half-lives of billions of years, affecting their use in dating, medicine, and nuclear energy.
How can you determine the half-life of a radioactive substance using a decay graph?
- Identify the initial amount on the y-axis.
- Find the y-value that is half of the initial amount.
- Locate the corresponding x-value (time) where the curve reaches this y-value.
- The x-value represents the half-life of the substance.
For example, if the initial y-value is 15 g, half-life corresponds to 7.5 g on the y-axis.
True or false:
All elements undergo radioactive decay at the same rate.
False
Decay rates vary depending on the isotope’s half-life.
What fraction of an original Carbon-14 sample remains after 17,190 years (three half-lives)?
Carbon-14 has a half-life of about 5,730 years.
1/8
The amount of the sample decreases from 1/2 to 1/4 to 1/8 over three half-lives.
True or false:
The rate of radioactive decay is affected by external conditions such as temperature or pressure.
False
Radioactive decay is independent of external conditions like temperature or pressure.
What type of graph represents radioactive decay?
An exponential decay graph.
The graph is exponential because the decay function involves raising a fraction (1/2) to the power of the number of half-lives elapsed.
The y-value decreases and approaches zero as the x-value increases.
Define:
Isotope
Atoms of the same element that have the same number of protons but different numbers of neutrons.
They have the same atomic number but differ in mass number, affecting their stability and behavior in nuclear processes.
True or false:
All isotopes of a given element are radioactive.
False
Only certain isotopes, called radioisotopes, are radioactive.
What primarily determines the stability of an isotope?
The ratio of neutrons to protons in the nucleus.
Too many or too few neutrons can make a nucleus unstable.
Define:
Radioisotope
An isotope with an unstable nucleus that undergoes radioactive decay.
Examples include Uranium-238 and Carbon-14.
List the three major types of radioactive decay.
- Alpha decay
- Beta decay
- Gamma decay
Other types include neutron radiation, positron emission (β⁺ decay), and electron capture. These processes are important in nuclear physics, medicine, and energy production.
Define:
Alpha particles
They consist of two protons and two neutrons released during alpha decay.
Alpha particles are equivalent to helium nuclei. They tend to be heavy and positively charged, but have low penetration power. They can be stopped by something as thin as a sheet of paper!
When does an alpha decay occur?
When a nucleus with too many protons emits an alpha particle (α).
List three applications of alpha radiation.
- Smoke detectors
- Analysis of rocks and soil composition
- Cancer treatment
Alpha particle X-ray spectroscopy (APXRS) is used by NASA to study the rocks of Mars.
TAT is a treatment for cancer that targets tumors with alpha radiation.
Define:
Beta decay
A type of radioactive decay where a radioisotope emits a beta particle (β), equivalent to an electron.
It increases or decreases the atomic number of a radioisotope by one, but does not change the mass.
What are beta particles?
High-speed, high-energy electrons (β⁻) or positrons (β⁺) emitted during beta decay.
These particles are produced when a proton is broken into a smaller particle. They have moderate penetration power, but can be stopped by aluminum.
Define:
Gamma decay
It is the release of high-energy photons from an unstable nucleus without changing its composition.
Gamma rays are electromagnetic waves with high energy but no mass. They can be dangerous to humans and can be stopped by thick lead.
How is gamma decay used in the medical field?
- Radiation therapy for cancer.
- Sterilizing equipment.
- Diagnostic imaging tracers.
Gamma rays can pass through human tissue, which allows for diagnostics and therapeutic uses. However, they must be used carefully because they have the potential to damage human tissue and DNA.
Compare the penetration power of alpha, beta, and gamma radiation.
- Alpha: low, stopped by paper.
- Beta: moderate, stopped by aluminum.
- Gamma: high, stopped by thick lead.
The penetration depends on the type of radiation and can determine the level of danger of that kind of radiation to humans.
Gamma rays can penetrate and ionize tissues, create free radicals, and cause cancers.