Atomic Structure Flashcards
What is radioactive decay?
The process in which unstable isotopes decay into other elements and give out radiation as they try to become more stable.
What is ionising radiation and ionising power?
Ionising radiation is radiation that knocks electrons off atoms, creating positive ions.
The ionising power of a radiation source is how easily it can do this.
Give a brief summary of alpha (α) particles.
An alpha particle is 2 neutrons and 2 protons (like a helium nucleus, an alpha particle can be written as a helium nucleus). The don’t penetrate very far into materials are are stopped quickly - they can only travel a few cm in air and are absorbed by a sheet of paper. Because of their size they are strongly ionising. When an alpha particle is emitted, the charge and mass of the nucleus decreases.
Give a brief summary of beta (β) particles.
A beta particles is a fast-moving electron released by the nucleus. Beta particles have virtually no mass and a charge of -1. They penetrate moderately far into materials before colliding and have a range in air of a few metres. They are absorbed by a sheet of aluminium. For every beta particle emitted, a neutron in the nucleus has turned into a proton. When a beta particle is emitted the charge increases but the mass remains the same as a neutron is changed into a proton ( a neutron and proton have the same mass).
Give a brief summary of gamma rays (γ).
Gamma rays are waves of electromagnetic radiation released by the nucleus. They penetrate far into materials without being stopped and will travel a long distance through air. They can be absorbed by thick sheets of lead or metres of concrete. They are weakly ionising because they tend to pass through rather than collide with atoms. Eventually they hit something and do damage.
What is a half-life?
The time taken for the number of radioactive nuclei in an isotope to halve.
What is activity?
The rate at which a source decays. It’s measured in becquerels (Bq).
Why is a short half-life dangerous?
A short half-life means the activity falls quickly, because the nuclei are very unstable and rapidly decay. Sources with a short half-life are dangerous because of the high amount of radiation they emit at the start, but they quickly become safe.
What are sources of background radiation?
- Radiaoctivity of naturally occuring unstable isotoopes which are all around us (e.g. food, buildign materials, rocks).
- Cosmic rays (radiation from space, mainly the sun).
- Radiation due to human activity (e.g. fallout from nuclear explosions, nuclear waste).
What is irradiation?
Irradiation is exposure to radiation. Irradiating something does not make it radioactive. High levels of irradiation can be dangerous.
What is contamination?
The presence of radioactive substances on surfaces or within solids, liquids or gases, where their presence is unintended or undesirable. Contaminating atoms might decay, releasing radiation which could cause you harm.
What are the risks to a human of using radiation ?
Radiation can enter living cells and ionise atoms or molecules within them. This can lead to tissue damage.
Lower doses tend to cause minor damage without killing the cells. This can give rise to mutant cells which divide uncontrollably. This is cancer.
Higher doses tend to kill cells completely, causing radiation sickness if a lot of cells all get killed at once.
What is nuclear fission?
A type of nuclear reaction that is used to release energy from large and unstable atoms by splitting them into smaller atoms. Usually, the nucleus has to absorb a neutron before it will split.
What is a chain reaction caused by nuclear fission?
If any neutrons released when an atom splits are moving slow enough to be absorbed by another nucleus, they can cause more fission to occur. This is a chain reaction. Uncontrolled chain reactions quickly lead to lots of energy being released as an explosion.
What happens in nuclear fusion?
In nuclear fusion, two lighter nuclei collide at high speed and join (fuse) to create a larger, heavier nucleus. Some of the mass of the lighter nuclei is converted to energy. This energy is then released as radiation. Fusion releases more energy than fission but fusion reactors are very expensive and hard to build.
