POM: Nuclear Chemistry Flashcards
Descibe the conditions under which a nucleus is unstable
Atomic number is greater than 83 (alpha decay)
Ratio of neutrons to protons is outside the zone of stability (beta deca)
Describe how transuranic elements are produced.
Transuranic elements are elements of atomic number 92 and above.
They are not naturally occurring, and can be synthesised with:
NUCLEAR REACTOR = neutron bombardment
- The elements neptunium (93), plutonium (94) and americium (95)
CYCLOTRONS = fusion reastions by particle accelerators
- Elements above 95
How is photographic film used to detect radiation?
- By the darkening of photographic film.
– Radiation badges are worn by laboratory workers handling radioactive substances
How is a cloud chamber used to detect radiation?
- Contains supersaturated water or alcohol vapour cooled with dry ice.
– As radiation travels through their air and vapour, it ionises surrounding air molecules. The
vapour molecules condense onto these ions, creating small droplets or cloud trails that reveal the path of the ionising radiation. particles form straight dense tracks; particles form thinner zigzag tracks; rays form even fainter tracks.
How is a scintillation counter used to detect radiation?
When certain substances re irradiated with , or rays, they emit a flash of light
(scintillation) which can be collected and amplified in a photomultiplier.
The electrical signal
generated is then counted electronically to measure the amount of radiation.
How is a Geiger-Muller counter used to detect radiation?
- This device uses ionising properties of radiation, and is only able to measure radiation.
– The ray enters the Geiger tube, collides with a gas molecule (e.g. argon) and ionises it,
knocking an electron out of it.
– The high voltage accelerates this electron so that it ionises more argon atoms in its path,
constituting an electrical pulse which is amplified and measured by an amplifier or counter.
How is Cobalt-60 an isotope used in industry?
Used to irradiate food materials to minimise spoilage and extend shelf life
- Food on a conveyor belt is gamma irradiated by passing it through a chamber containing a safely shielded Co-60 source.
Sterilise medical supplies such as dressings and bandages.
What are the properties of Cobalt-60?
Co-60 is chemically inert and is a potent gamma emitter.
Gamma rays can easily
penetrate hermetically sealed packaging and the contents, killing harmful microbes such as bacteria, viruses and fungi. They have sufficient energy to destroy bacteria but not enough to make food radioactive.
Co-60 has a reasonably long half-life of 4-6 years, to minimise replacement.
However, there are concerns that gamma radiation can destroy vitamin content in food and
may lead to the formation of harmful compounds in the food. In addition, workers must be protected from irradiation.
How is Technetium-99mm an isotope used in medicine?
Used for medical diagnosis.
The Tc-99m is attached to a biological molecule that concentrates in the organ to be investigated.
A scintillation counter measures the distribution of Tc-99m which can be used to detect and pinpoint blood clots, constrictions and other circulation disorders.
What are the properties of Technetium-99m?
Short half-life of 6 hours.
It rapidly decays and so causes minimal damage to the patient.
Emits low energy gamma radiation, which causes minimal damage to healthy
cells, but can still be detected in the body by a gamma ray sensitive camera.
Quickly eliminated from the body.
Relatively reactive, so it can be reacted to form a compound with chemical
properties that leads to concentration in the organ of interest such as the heart, liver,
lungs or thyroid.
What are benefits of he use of radioactive isotopes in identified industries and medicine?
- Non invasive diagnostic techniques
- Make monitoring equipment more sensitive and precise
- Carry out tasks more efficiently and reliably
- Perform tasks that were not otherwise possible
What are problems of he use of radioactive isotopes in identified industries and medicine?
- Harmful to humans and all other life forms by upsetting the delicate balance among the complex chemical reactions occurring in living cells.
- Continued exposure to radiation can lead to diseases
- Nuclear reactors produce nuclear waste which must be disposed safely
