Radioactivity and Particles

Radioactivity and Particles

1. RADIOACTIVITY

   • At the Centre of Every Atom is a Nucleus
     • NUCLEUS OF AN ATOM CONTAINS PROTONS AND NEUTRONS.MAKES UP MOST OF THE MASS OF THE ATOM, BUT TAKES UP VIRTUALLY NO SPACE
     • THE NUMBER OF PROTONS IN THE NUCLEUS IS CALLED THE ATOMIC NUMBER, OR PROTON NUMBER. THE TOTAL NUMBER OF PROTONS AND NEUTRONS I THE NUCLEUS IS CALLED THE MASS NUMBER, OR NUCLEON
     • THE ELECTRONS ARE NEGATIVELY CHARGED AND REALLY REALLY SMALL. THEY WHIZZ AROUND THE OUTSIDE OF THE ATOM. THEIR PATHS TAKE UP A LOT OF SPACE, GIVING THE ATOM ITS OVERALL SIZE
     • ATOMS ARE NEUTRAL, SO THE NUMBER OF PROTONS= THE NUMBER OF ELECTRONS
   • Isotopes are Atoms with Different Numbers of Neutrons
     • MANY ELEMENTS HAVE A FEW DIFFERENT ISOTOPES. ISOTOPES ARE ATOMS WITH THE SAME NUMBER OF PROTONS BUT A DIFFERENT NUMBER OF NEUTRONS
       • USUALLY, EACH ELEMENT ONLY HAS ONE OR TWO STABLE ISOTOPES- LIKE CARBON- 12. THE OTHER ISOTOPES TEND TO BE RADIOACTIVE- THE NUCLEUS IS UNSTABLE, SO IT DECAYS AND EMITS RADIATION. CARBON-14 = UNSTABLE
   • Radioactive Decay is a Random Process
     • NUCLEI OF UNSTABLE ISOTOPES BREAK DOWN AT RANDOM. CAN'T PREDICT OR MAKE IT DECAY
       • WHEN NUCLEUS DECAY IT SPITS OUT ONE OR MORE TYPES OF RADIATION- ALPHA, BETA, GAMMA OR NEUTRONS
   • Background Radiation is Everywhere All the Time
     • COMES FROM- SUBSTANCES ON EARTH- AIR, FOOD, ROCKS ETC
       • SPACE- COSMIC RAYS
         • LIVING THINGS
           • HUMAN ACTIVITY- FALLOUT FROM NUCLEAR EXPLOSIONS, NUCLEAR WASTE

2. IONISING RADIATION

   • Nuclear Radiation Causes Ionisation
     • NUCLEAR RADIATION CAUSES IONISATION BY BASHING INTO ATOMS AND KNOCKING ELECTRONS OFF THEM. ATOMS TURN TO IONS- IONISATION.
     • FURTHER, IT CAN PENETRATE THE LESS IONISING IT IS
     • IONISING RADIATION CAN BE DETECTED USING EITHER A GEIGER- MULLER DETECTOR OR PHOTOGRAPHIC FILM
   • Alpha Particles are Helium Nuclei
     • 2 PROTONS 2 NEUTRONS- BIG, HEAVY, SLOW-MOVING
     • DON'T PENETRATE FAR. STOPPED BY PAPER
     • STRONGLY IONISING, BASH INTO A LOT OF ATOMS AND KNOCK ELECTRONS
     • POSITIVE CHARGED, ALPHA PARTICLES ARE DEFLECTED BY ELECTRIC AND MAGNETIC AND MAGNETIC FIELDS
       • EMITTING AN ALPHA PARTICLE DECREASES THE ATOMIC NUMBER OF THE NUCLEUS BY 2 AND THE MASS NUMBER BY 4
   • Beta Particles are Electrons
     • ELECTRON WHICH HAS BEEN EMITTED FROM THE NUCLEUS OF AN ATOM WHEN A NEUTRON TURNS INTO A PROTON AND AN ELECTRON
       • THEY ARE SMALL AND FAST. THEY GET DEFLECTED AS THEY ARE NEGATIVELY CHARGED BY ELECTRIC AND MAGNETIC FIELDS
     • WHEN EMITTED, THE NUMBER OF PROTONS IN THE NUCLEUS INCREASES BY 1. THE ATOMIC NUMBER INCREASES BY 1 BUT THE MASS NUMBER STAYS THE SAME
   • Gamma Rays are Very Short Wavelength EM Waves
     • NO MASS- JUST ENERGY
       • PENETRATE LONG WAY INTO MATERIALS WITHOUT BEING STOPPED
       • NO CHARGE= NOT DEFLECTED BY ELECTRIC OR M.F.
         • EMISSION HAS NO EFFECT ON THE ATOMIC OR MASS NUMBERS OF THE ISOTOPES. IF THE NUCLEUS HAS EXCESS ENERGY, IT LOSES ENERGY BY EMITTING A GAMMA RAY
     • WEAKLY IONISING- PASS-THROUGH RATHER THAN BASH INTO OTHER ATOMS.

3. INVESTIGATING RADIATION AND NUCLEAR EQUATIONS

   • Penetration of Radiation
     • GEIGER-MULLER DETECTOR, MATERIAL, RADIOACTIVE SOURCE [SET UP] RECORD BACKGROUND RADIATION THEY WITH THE RADIOACTIVE SOURCES MEASURE THE PENETRATION WITH DIFFERENT MATERIALS. MINUS THE BACKGROUND RADIATION.
       • IF THE COUNT DROPS= MATERIAL ABSORBS.
         • IF ZERO= COMPLETE ABSORBTION
   • Balancing Nuclear Equations
     • THE OVERALL CHARGE AND MASS HAVE TO BE THE SAME AFTER A NUCLEAR REACTION AS THEY WERE BEFORE
     • THE CHARGE ON A NUCLEUS OR PARTICLE IS EQUAL TO THE ATOMIC NUMBER, AND ITS MASS IS EQUAL TO THE MASS NUMBER. THE TOTALS OF THE ATOMIC AND MASS NUMBER ARE THE SAME ON BOTH SIDES OF THE EQUATIONS

4. HALF-LIFE

   • Radioactivity of a Sample Always Decreases Over Time
     • ACTIVITY DROPS OFF AT DIFFERENT RATES. SOME ISOTOPES= FEW HOURS AND SOME MILLIONS OF YEARS
       • ACTIVITY NEVER EQUALS ZERO
         • SHORT HALF-LIFE= ACTIVITY FALLS QUICKLY
         • LONG HALF-LIFE= ACTIVITY FALL SLOWER
   • HALF-LIFE IS THE TIME TAKEN FOR HALF OF THE RADIOACTIVE ATOMS NOW PRESENT TO DECAY
   • Measuring the Half-Life of a Sample Using a Graph
     • HALF-LIFE IS FOUND FROM THE GRAPH, BY FINDING THE TIME INTERVAL ON THE BOTTOM AXIS CORRESPONDING TO A HALVING OF THE ACTIVITY ON THE VERTICLE AXIS

5. USES OF NUCLEAR RADIATION

   • Medical Tracers Use Beta or Gamma Radiation
     • SOURCE WHICH EMITS BETA OR GAMMA IS INJECTED INTO THE PATIENT. IT CAN PENETRATE THROUGH THE SKIN AND BE DETECTED OUTSIDE THE BODY.
     • THIS IS USED TO CHECK ORGANS. THE SOURCE HAS A SHORT HALF-LIFE SO IT DISAPPEREAS QUICKLY
   • Radiation is Also Used to Treat Cancer
     • RADIOTHERAPY KILLS THE CANCER CELLS AND STOPS THEM DIVIDING- HIGH DOSE OF GAMMA CAREFULLY DIRECTED TO ZAP THE CELLS IN THE TUMOR WHILE MINIMISING THE DOSE TO THE REST OF THER BODY
   • Food and Equipment can be Sterilised Using Gamma Rays
     • FOOD CAN BE IRRADIATED WITH A HIGH DOSE OF GAMMA RAYS TO KILL ALL MICROBES SO THAT IT DOESN'T GO BAD AS QUICKLY
     • MEDICAL EQUIPMENT CAN BE STERILISED BY GAMMA RAYS
     • IRRADIATION DOESN'T NEED HIGH TEMPERATURES, SO NO HEAT DAMAGE
   • Radiation is Used in Industry for Tracers and Thickness Gauges
     • GAMMA RAYS ARE USEED IN INDUSTRY TO DETECT LEAKS IN UNDERGROUND PIPES
       • SOURCE FLOWS IN PIPE AND DETECTED EXTERNALLY. MORE DETECTED= CRACK
       • SHORT HALF-LIFE DOESNT AFFECT ANYWHERE ELSE
     • BETA= THICKNESS OF PAPER

6. RISKS FROM NUCLEAR RADIATION

   • Ionising Radiation Can Damage Cells and Tissues
     • ALPHA CAN'T PENETRATE OUT OF THE BODY AND CAN DO SERIOUS INTERNAL DAMAGE
     • LOWER DOSES= MINOR DAMAGE WITHOUT KILLING CELLS. BUT CAN MUTATE INTO CANCER
     • HIGHER DOSES= TEND TO KILL CELLS COMPLETLY, CAUSING RADIATION SICKNESS IF A LARGE PART OF YOUR BODY IS AFFECTED AT THE SAME TIME
   • Exposure to Radiation is called Irradiation
     • OBJECTS NEAR A RADIOACTIVE SOURCES ARE IRRADIATED THEY'RE EXPOSED TO IT. IT DOESN'T MAKE IT RADIOACTIVE
   • Contamination is Radioactive Particles Getting onto Objects
     • UN WANTED RADIOACTIVE ATOMS GET ONTO AN OBJECT
     • THEY CAN GET INTO YOUR BODY
   • Radioactive Waste is Difficult to Dispose of Safely
     • HIGH-LEVEL WASTE IS DANGEROUS- HAS TO BE TREATED CAREFULLY- IN GLASS BOX IN METAL CONTAINERS
     • HAS TO BE NO EARTHQUAKES NEAR [GEOLOGICALLY STABLE] AS THE SUBSTANCE CAN LEAK OUT

7. NUCLEAR FISSION AND FUSION

   • Nuclear Power Stations use Nuclear Fission Chain Reactions
     • NUCLEAR FISSION IS THE SPLITTING OF ATOMS, WHICH RELEASE ENERGY- NEEDS A NUCLEAR REACTOR
     • SLOW-MOVING NEUTRON IS ABSORBED BY A URANIUM-235 NUCLEUS, THE NUCLEUS, CAN SPLIT
     • IT SPITS OUT A SMALL NUMBER OF NEUTRONS THESE CONTINUES THE CHAIN
     • IT FORMS TWO NEW DAUGHTER NUCLEI, BOTH LIGHTER THAN URANIUM
     • THESE ARE RADIOACTIVE= PROBLEM WITH NUCLEAR POWER
     • WITH EACH SPLIT IT GIVES OFF A LOT OF ENERGY- KINETIC ENERGY STORES
     • REACTOR TRANSFERS IT INTO THERMAL ENERGY TO TURN TURBINE
   • Nuclear Reactions Have to Work Safely
     • MODERATOR= GRAPHITE- SLOWS THE NEUTRONS
       • CONTROL RODS= BORON- ABSORBS EXCESS NEUTRONS
         • SHIELDING= ABSORBS IONISING RADIATION
   • Nuclear Fusion- Joining Small Nuclei
     • IT IS THE OPPOSITE OF FISSION. NUCLEAR FUSION, 2 LIGHT NUCLEI COLLIDE AT HIGH SPEED AND JOIN TO CREATE A LARGER, HEAVIER NUCLEUS
     • GIVES A LOT OF ENERGY IT NEEDS HIGH PRESSURES AND TEMPERATURES- THIS IS BEACUSE THE POSITIVELY CHARGED NUCLEI HAVE TO GET VERY CLOSE TO FUSE.
     • THE REACTORS ARE HARD AND EXPENSIVE TO BUILD

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