Atomic Structure Flashcards
(21 cards)
Describe the current model of the atom
Nucleus is tiny but makes up most of the mass of the arom. Contains protons (positively charged - they have a +1 relative charge) and neutrons (which are neutral, with a relative charge of 0) which gives it an overall positive charge. Its radius is about 10,000 times smaller that the radius of the atom
Describe Alpha radiation particles?
Made up of helium Nucleus. Do not penetrate very far, stopped quickly - they can only travel a few cm in the air and are absorbed by a sheet of paper. Strongly ionising because of size
Describe Beta radiation particles?
High energy electrons. Have a range of a few metres in the air. Absorbed by a sheet of aluminium.
Describe gamma rays?
Electromagnetic waves. No charge. Very penetrating, least ionising. Can be absorbed by thick lead
What is alpha decay?
Alpha decay decreases the charge and Mass of the Nucleus.
4
He
2
What is beta decay?
Beta decay increases the charge of the Nucleus
0
e
-1
What is gamma ray?
Gamma rays dont change the charge or mass of the nucleus
What is half life?
The time for the number of radioactive nuclei, the activity of the count rate to halve
Give three sources of background radiation?
1) radioactivity of naturally occurring unstable isotopes which are all around us - in air, im food, building materials.
2) radiation from space, cosmic rays.
3) radioactive due to human activity.
What is exposure to radiation called?
Irradiation.
What is contamination?
Contamination is radioactive particles getting onto objects
Seriousness of irradiation and contamination depends on source
1) outside the body, gamma and beta sources are most dangerous. This os because beta and gamma can penetrate through the skin and can get to delicate organs. Alpha cannot.
2) inside the body, alpha sources are most dangerous because they do all their damage in very localised area. So contamination, rather that irradiation, is the major concern when working with alpha sources
What are the risks of using radiation
1) Radiation can enter living cells and ionise atoms and molecules within them. Leads to tissue damage.
2) causes cancer
3) causes radiation sickness (tired, vomit etc)
Uses of gamma sources radioactivity?
Gamma sources are usually used in medical tracers. The radioactive substance flows in and out of a normal kidney, so the detector reading goes up and down. For a blocked kidney the reading goes up and stays up.
Describe how radiotherapy is used to treat cancer?
Gamma rays are directed carefully and at the right dosage to kill the cancer cells without damaging too many normal cells.
Benefits of the uses of radiotherapy?
Can be used to diagnose life-threatening conditions and get rid of cancer
Risks of the uses of radiotherapy?
Tracers have a small risk of cancer, side effects.
Describe nuclear Fission?
Nuclear fission is the splitting a large, unstable nucleus into a small nucleus. Fission is more likely to happen when a nucleus is absorbed by a nucleus of uranium or plutonium.
What is a chain reaction?
A chain reaction is when the nucleus is split and two or three neutrons are released. Theses neutrons will be absorbed by other nuclei causing them to split.
What is nuclear fusion?
Light and nuclei collide at high speed and join to make larger nuclei.
Why are fusion reactors hard to build?
Because two positively charged nuclei will repel each other, the temperature and pressure needed for fusion is high, so they are hard/expensive to build.
