Radioactivity Flashcards
(30 cards)
What is meant by the term nuclide? how is it represented/ notated?
A nuclide is any particular type of nucleus, characterised by the no. of protons and neutrons it has
NOTATION:
4 —> Mass number
He —> Element symbol
2 —> Atomic number
What is ionisation?
The process of gaining or losing one or more electrons
What are the 2 types of naturally occurring nuclides you can have?
These naturally occurring nuclides can be either STABLE or UNSTABLE :
- Nuclei that are stable will continue to exist indefinitely
- Nuclei that are unstable, will eventually “decay”; emitting radiation as they do- they are therefore described as “radioactive”
What are the types of radiation an unstable nuclei can emitt?
- Alpha
- Beta
- Gamma
What happens to an unstable nuclei after it decays?
1 of 2 things can happen:
1) An unstable nucleus will decay into a STABLE nucleus
OR
2) An unstable nucleus will decay into a nuclide which is ALSO RADIOACTIVE
(This may lead to a series of decay/ “decay chain”, which ends when a stable nuclide is reached)
What is radioactive decay?
A RANDOM process in which an unstable nucleus loses energy to regain stability by emitting radiation/ a type of emission (may involve more than one type of emission)
What are the characteristics of alpha particle?
- An alpha particle is a helium nucleus (2 protons and 2 neutrons)
- They have the smallest range (roughly a few cm)
- They are the most ionising form of radiation; they have a +2 charge; can easily drag e- away from things
- They are blocked by almost everything, including paper and skin
- When a nucleus emits an alpha particle: its MASS NUMBER DECREASES by 4 & its ATOMIC NUMBER DECREASES by 2
What are the characteristics of beta particles?
- Beta particles are high speed electrons (have mass 0 and charge -1)
- They have a medium range (up to 1m)
- They have medium ionising power (their -1 charge isn’t quite as good as alpha’s +2 charge at knocking electrons off atoms)
- They are blocked by aluminium (thin metal)
- When a nucleus undergoes beta decay 1 neutron becomes a proton and an electron is emitted; its MASS NUMBER STAYS THE SAME & its ATOMIC NUMBER INCREASES by 1
What are the characteristics of gamma particles?
- Gamma rays are photons (electromagnetic waves); have a charge of 0 and a mass of 0
- They have the longest range (they can travel much, much more than 1m)
- They are the least ionising (in order for a a gamma ray to know an electron off, it needs to hit the electron directly and give it so much energy that it leaves the electron shell- this is very unlikely)
- They are blocked by big sheets of lead or other high-atomic-number heavy materials
- When a nucleus emits a gamma ray, its MASS AND ATOMIC NUMBERS DON’T CHANGE
What effect does an electric field have on Alpha, Beta and Gamma particles?
-Both alpha and beta particles are charged (a = +2, b = -1)
-Deflect in the presences of electric fields
(charged bodies experience forces when they are in electric fields)
-They are oppositely charged; they deflect in opposite directions
-Beta particles have a lower mass; beta particles deflect more
-Gamma rays have no charge; DO NOT DEFLECT in the presence of electric fields
What effect does a magnetic field have on Alpha, Beta and Gamma particles?
-Both alpha and beta particles are charged (a = +2, b = -1)
-Deflect in the presences of magnetic fields
(moving charges experience forces when they are in magnetic fields)
-They are oppositely charged; they deflect in opposite directions
-Beta particles have a lower mass; beta particles deflect more
-Gamma rays have no charge; DO NOT DEFLECT in the presence of magnetic fields
What factors contribute to the fact that beta particles deflect more than alpha particles?
- Beta particles have a lower mass than alpha particles
- therefore, have a much higher speed than alpha particles
- (On the other hand alpha particles have a higher charge than beta particle, and so experience twice as much force in an electric field)
- However, the effect of charge is less dominant than that of mass (effect of mass > charge > speed), therefore, OVERALL, beta articles deflect more than alpha particles
What is meant by the term “background radiation”?
Ionising radiation that is present at a low level in the human environment
-most of it is naturally occurring, although a small percentage is due to human activities
Give examples of natural sources of background radiation
-Radon gas from the ground
-Rocks and buildings
-Cosmic rays
-Food and drink
(makes up 80% of totla)
Give examples of artificial sources of background radiation
-Medical procedures
-Nuclear power and nuclear weapons testing
(makes up 20% of total)
In general what sort of damaged can occur from nuclear radiation inside the body?
- Nuclear radiation can damage human tissue
- It ionises atoms and molecules- affects the chemical reactions tat take place in cells
- Ionisation can damage the delicate strands of DNA
- Causes cells to malfunction- in some cases, leads to uncontrollable cell division/ cancer
- High doses destroy living cells
- causes death in extreme cases
How hazardous is alpha radiation compared to the other forms, inside and outside the body?
INSIDE:
- the most hazardous
- highly ionising
- will damage cells
OUTSIDE:
- Not hazardous
- Alpha particles cannot penetrate the skin
How hazardous is beta radiation compared to the other forms, inside and outside the body?
INSIDE:
- Less hazardous than alpha
- less ionising
- But, will still cause some cell damage
OUTSIDE:
- Hazardous
- beta particles can typically penetrate the skin
- damages tissue under the skin
How hazardous is gamma radiation compared to the other forms, inside and outside the body?
INSIDE:
- Generally less hazardous than alpha/ beta
- It is less ionising
- much of it will pass straight through cells without damaging them
OUTSIDE:
- Hazardous
- gamma rays can easily penetrate the skin and cause damage anywhere in the body
Give 3 applications for ionising radiation in everyday life
- Sterilisation
- Medical tracers
- Thickness gauge
How is ionising radiation used for sterilisation? what type of radiation an half-life is suitable for this?
- Medical equipment such as syringes and some foods are exposed to high doses of ionising radiation to kill bacteria
- Particularly useful for plastic items- cannot be sterillised through heating
- Gamma is used; it is the most penetrating- can reach and sterilise all parts of the equipment/ food
- The half-life should be long (years); the radiation source does not need to be replaced frequently
How is ionising radiation used for medical tracers? what type of radiation an half-life is suitable for this?
- Radioactive nuclides that are swallowed/ injected into the body- continue to emit radiation which is detected from outside the body to observe the movement of the tracer through an organ, to observe how the organ is functioning
- Requires radiation which causes minimal ionisation and easily penetrates the body; gamma is used
- Half- life should be long enough for the test to be completed, but the patient’s exposure to radiation is minimised; the half life need to be short (hours)
How is ionising radiation used for a thickness gauge? what type of radiation an half-life is suitable for this?
- When sheet material (such as paper or cooking foil) is made in a factory, the sheet thickness needs to be kept within an acceptable range of values. This can be done by positioning a radioactive source on one side of the moving sheet and a radiation counter on the other side
- needs to be able to penetrate the sheet, but be significantly affected by the changes in sheet thickness (alpha cant penetrate and gamma would pass through and be unaffected by small changes in thickness- Beta is used
- Half-life should be long; the radiation source does not need to replaced frequently (years)
What is meant by the term “half-life”?
The half life is the average time it takes for the number of nuclei in a radioactive sample to halve
