Topic 7- Radioactivity Flashcards
What does a nucleus of an atom contain and what is its overall charge?
protons and neutrons, therefore the overall charge is positive.
what makes up most of the mass of an atom?
the nucleus, however, it virtually takes up no space
where are electrons in an atom?
they are around the structure
what is the proton number/atomic number?
the number of protons
what is the total number of protons and neutrons together?
the mass number or nucleon number
what is an isotope?
an atom of an element which has a different number of neutrons in the nucleus (different mass/nucleon number) but the same number of protons (same proton number)
What are alpha, beta and gamma?
Ionising radiations emitted from unstable nuclei in a random process.
What is the nature of alpha and its properties?
Helium nucleus Mass= 4 Charge= +2 Ionising power= very strong Penetrating power= weak, travels the least before ionised as it is absorbed by paper.
What is the nature of beta and its properties?
High speed electron Mass= 0 Charge= -1 Ionising power= medium Penetrating power= travels a little before ionised as it is absorbed by a sheet of aluminium.
What is the nature of gamma and its properties?
An electromagnetic wave Mass= 0 Charge= 0 Ionising power= weak Penetrating power= travels the furthest before ionised as it is absorbed by thick lead.
What happens to the proton and mass number if alpha is emitted from an unstable nucleus?
Atomic number= decreases by 2
Mass number= decreases by 4
What happens to the proton and mass number if beta is emitted from an unstable nucleus?
Proton number= increases by 1
Mass number= stays that same
What happens to the proton and mass number if gamma is emitted from an unstable nucleus?
No effect
What is ionising radiation detected by?
Geiger muller tube and counter.
How can a Geiger muller tube and counter be set up to count ionising radiation?
- tube is filled with an inert gas (e.g. Argon) and has a thin electrode going through it.
- alpha/beta particles are passed through, ionising the air and in turn making the tube conduct.
- this creates a current, which produces a voltage pulse that is amplified.
- one voltage pulse= one ionising radiation.
Apart from using a GM tube and counter, how can ionising radiation be detected?
Photographic film gets darker when it absorbs radiation.
What are sources of background radiation?
Medicinal equipment
Cosmic waves
Rocks
What happens to the activity of a radioactive source over time?
It decreases
What is radiation measured in?
Becquerels
What is the half life of a radioactive material?
The time taken for half of the radioactive atoms present now to decay.
Uses of radioactivity?
Travers
Medical tracers
Radiotherapy
Archaeological specimens and rocks
How are tracers used?
A leak in an underground pipe can be detected by piping through a gamma source. Where there is a leak or crack, gamma will collect and accumulate, which will be shown as high activity on the detector.
How is radiation used in medical tracers
A radioactive source (e.g. Beta or gamma) is injected into a patient and will build up at a blockage so the problem can be detected.
How is radioactivity used in radiotherapy?
Used to destroy cancerous cells.
How is radioactivity used in specimens and rocks?
Carbon dating
The amount of radiation from the object is measured and then the half life of the carbon is used to see how old the object is.
Why is radiation dangerous?
- Mutations: damages the cell’s DNA structure which is the passed on when replicated.
- Damage to cells and tissues: prevents the, fro, functioning properly
- Can poison ecosystems and land when it is disposed into water or buried under ground.
How can you reduce the risks that come with radiation?
- wear protective clothes
- work with radiation in special cabinets
- use materials that decay quickly
- limit exposure time
What were the steps of Geiger and Marsden’s alpha scattering experiment?
1) beam of alpha particles shined through a thin gold foil
2) most went through
3) some were deflected back at large angles
What were the conclusions made from the alpha scattering experiment
- most of the mass if concentrated and at the centre= an empty space
- nucleus must be very small since very few alpha particles were largely deflected
- nuclei must be positive as positive alpha particles were deflected
How can the nucleus of a U-235 be split and heat does it release?
-fission: absorbs a neutron and splits.
Splits: releases energy in the form of KE.
What happens when a U-235 absorbs a slow moving neutron?
The nucleus splits into two daughter nuclei and a small number of neutrons.
How can a chain reaction be set up?
- neutrons released from U-235 are absorbed by other U-235 nuclei= causes it to split.
- Even more neutrons are released and the process is repeated= chain reaction
What do control rods do?
Made of boron and are used to control reactions.
Reaction too fast: placed in reactor to absorb excess neutrons
Too slow: removed to free up neutrons.
What does a moderator do?
Ensures neutrons are right speed to be absorbed and cause U-235 to split.
Why is a nuclear reactor cased in a concrete shield?
Prevents any nuclear leaks.
What is the coolant used for in reactors?
The liquid that absorbs the heat from the reaction.
-heats water—> steam
Which turns a turbine and then a generator= electricity.
