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Science P3 Topic 3
GCSE edexcel further additional physics: ionising radiation from radioactive sou
| Question | Answer |
|---|---|
| What is the atomic number of an element? | the number of protons, which is equal to the number of electrons |
| What is the mass number of an element? | the total number of nucleons- protons and neutrons |
| What happens in beta minus decay? | In beta minus decay, a neutron becomes a proton plus an electron- this increases the atomic number by one but leaves the mass number unaffected |
| What are beta particles and how penetrating are they? | Beta particles are high energy electrons that are ionising and can penetrate paper but not thin sheets of metal |
| What happens in beta plus decay? | In beta plus decay, a proton becomes a neutron plus a position. This decreases the atomic number by one but leaves the mass number unaffected |
| What is a positron? | A positron is the antimatter particle of an electron so has a positive charge |
| What happens in alpha decay? | In alpha decay, the atomic number decreases by two and the mass number decreases by four |
| What are the properties of alpha particles? | An alpha particle is made up of two protons and two neutrons. They are very ionising as their large size allows them to dislodge electrons from atoms they collide with easily. They have a short penetration distance -stopped by a few millimetres of paper |
| What happens in gamma decay? | Gamma radiation has no mass so causes no change to the atomic or mass number of an atom. The nucleus becomes more stable when releasing gamma rays as it loses energy |
| What is neutron radiation? | Radioactive decay can result in a neutron being ejected. Neutrons are very penetrating but aren’t ionising |
| What are isotopes? | Isotopes are atoms of a single element that have different numbers of neutrons, so have different mass numbers |
| What is the N-Z curve? | The N-Z curve graph shows the position of different radioactive isotopes in terms of their number of neutrons (N) against their number of protons (Z) |
| What is the stability line and where does it end? | The stability line is the line of isotopes that are stable so won’t decay (ends at Z=82) |
| If a nucleus has a high number of protons, Z, (above 82), what kind of radioactive decay will it normally undergo? | Alpha decay |
| An isotope above the stability line will normally undergo what kind of radioactive decay? | Beta minus decay, as it has too many neutrons to be stable |
| An isotope below the stability line will normally undergo what kind of radioactive decay? | Beta plus decay, as it has too many protons to be stable |
| What is a quark? | A particles from which neutrons and protons are made - they each contain three quarks |
| What are the masses and charges of the different flavours of quarks? | Up quark = mass 1/3, charge +2/3 Down quark = mass 1/3, charge -1/3 |
| What flavours of quarks do protons consist of and how does this influence its features? | A proton consists of two up quarks and one down quark, so has a mass of 1 and a charge of +1 |
| What flavours of quarks do neutrons consist of and how does this influence its features? | A neutron consists of one up quark and two down quarks, so has a mass of 1 and a charge of 0 |
| Why can protons and neutrons turn into each other? | Because quarks can change flavour |
| What is B- decay in terms of quarks? | In beta minus decay a down quark changes into an up quark, so a neutron becomes a proton and an electron |
| What is B+ decay in terms of quarks? | In beta plus decay an up quark changes into a down quark, so a proton becomes a neutron and a positron |
| What are some dangers of ionising radiation? | • can kill cells and tissues • can cause mutations to the structure of DNA, which may be copied to new cells, causing cancers- this mutation could be passed on to next generation • can cause burns- beta burns on the surface, gamma burns are deeper |
| What are some precautions taken to avoid the dangers of ionising radiation? | •limited exposure time •radioactive sources are kept in lead-lined containers (shielding) •Sources are handled with tongs, not pointed at people •Protective clothing is worn •The dosage of radiation given to patients is low |
| What are some uses of ionising radiation in medicine? | •Radiotherapy treats cancer cells and shrinks tumours (palliative care) •Can be applied internally - beta emitter, such as iodine-131 - or externally with a gamma/x ray source •Cancers can be diagnosed using a tracer •PET scan after to locate tracer |
| Why do isotopes in PET scanners have to be produced nearby? | the isotopes also have a short half-life, to ensure that other parts of the body are affected as little as possible so they are made near to where they are used |
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