P7 Radioactivity

P7 Radioactivity

1. 7.1 Atoms and radoiation

   • A scientist called Marie Curie investigated uranium salts after a friend of hers noticed they had an effect on photographic plates. She and her husband pierre investigated and discovered radioactivity
   • A counter called a Geiger counter is used to messure radiocativity, it clicks every time a radioactive particles enters
   • A physist called Ernest Rutherford discovered 2 types of radiation alph and Beta and later gamma radiation was discovered
   • Radioactive deacay is ramdom and cannot be predicted

2. 7.3 Changes in the neucleaus

   • Alpha
     • Can't penertrate through paper
     • Conatians two protona and 2 neutrons so has the charge 2+
     • Durring decay it loses 2 protons and 2 neutronsin the form of an alpha particle
       • Its atomic number goes down by two and its mass number goes down by 4
       • Its mass and the charge of the neucleaus are both reduced
   • Gamma
     • Gamma radition is electromagnetic raditation from the neucleaus of an atom
     • The mass number and charge remain the same
   • Beta
     • Can pernertrate throught paper
     • A beta particle is where a neutron changes into a protone and an electron which is then emitted
     • The atomic number goes up by 1, by the mass stays unchanged
   • An isotope is an atom with the same number protons but a different number of neutrons

3. 7.2 The discovery of the neuclus

   • Rutherford and some other scientist did the gold foil exsperiment and discorvered that the plum pudding model was wrong so created the atom model as we know it today
   • Atoms have a small positivly charged neucleus where the atoms mass is located

4. 7.4 More about Alpha beta and Gamma radiation

   • Penertrating power
     • Alpha particles have the weekest penertrating power and can be stopped by paper
       • Its range is about 5cm
     • Beat radiation can be stopped by aluminum sheets (5mmthick) and lead sheets (2-3mm thick)
       • Its range is about 1m
     • Gamma radiation has the strongest penertrating power and can olny be stopped by thick lead (serveral cm thick) or concrete(1m thick)
       • Its range is unlimeted
   • Radioactive dangers
     • Durring radiation atoms can become irradiated which is where the radiation knocks electrons out of the atoms in a prosses called ironisation
     • When a substance comes into contact with a radioactive substance it is called radioactive contamination
     • Iornisation can damedge tissue in the body so strict safety rules are used when handeling radioactive substances
     • Ways to reduce ionising radiation for those working with substances that emit it
       • Keeping far away from the source
       • Spening as little time in contact with it as possible
       • Sheilding themselves by staying behind large concrete walls/thick lead plates
   • Radiation is used in smoke alarms and thickness detectors

5. 7.5 Activity and half life

   • The activity of a source is the number of unstable atoms that decay per second
   • The half life of a substance is the amount of time it takes for the number of radioactive isotopes to halve
   • The count rate after n half-lives = the initial count rate/2^n
   • The number of atoms in a radioactive isotope and the count rate both decreace by half every half-life

6. P6 Neuclear radiation in medicine

   • Radioactive tracers are used used to track the flow of substances through a person and to see where they may be blockedges or leeks
   • Gamma radiation is used in gamma cameras to take pictures of internal organs
   • A narrow beam of gamma radiation is used to destroy cancerous cells
   • Radioactive implants have been used to destroy cancerous cells

7. 7.7 Nuclear fission

   • It is the splitting open of a nucleus to form two smaller nuclei durring which energy in the form of gamma radiation and kinetic energy and two or three neutrons are release
   • The neutrons that are releaced at the end of the reaction bump into other atoms causing fission to occur there and causing a chain reaction
   • Nuclear reactors
     • Uranium rods are used as the fuel. A neutron is fired at them and this sets of the chain reaction. Control rods are used to absorb exsess neutrons and control the rate of the ration. Water surrounds them and moves around the rods to cool them and transport the heat energy to more water which turns to steam turning a turbine and generating electrisity

8. 7.8 Nuclear Fusion

   • It is the prosses of forcing two atoms close enougth together that they form 1 larger neucleus
   • Fusion is what happends in stars and the sun It is able to happen hear as it is hot eneogth so the atoms are plasma and ther is enegth pressure
   • Scientist are trying to make fusion reactors however it is very hard to recreate and more energy is put in than is made. however if it is possible then it would be good as the fuel needed is water and the waste is helium which is harmless

9. 7.9 Nuclear issues

   • After fuel rods are used they are radiocative and must be stored for thousands of years before they become harmless
   • There have been some awful acidents with nuclear rectors like Chernobyl and fukushima

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