11 Definition of Radioactive Isotope This occurs when the ratio of Neutrons to protons is too great or too small, and the atom spontaneously attempts to become stableExample carbon has five radioactive isotopesC-10, C-11, C-14, C-15, C-16
12 no. protons and neutrons Carbon 14Atomic Mass -no. protons and neutronsC146Atomic Number -No. protons
13 Ion An atom or molecule which has lost or gained one or more electrons An ion will have a positive or negative electrical charge
17 X-RaysProduced by accelerating electrons from a cathode onto an anode inside an evacuated glass tube. Less than 1 % of energy converted to x- rays, rest to heat.X-rays have the same physical properties as gamma photons.
19 Energy of Ionising radiation The energy of Alpha, Beta and Gamma radiations is measured in ELECTRON VOLTS eV, normally keV and MeV1eV = 1.6 x JHigher energy = more penetrating (for a given type of radiation)
21 Shielding Materials Alpha particles – Paper, dead layer of skin Beta particles – 1 cm perspex or tissueGamma Photons – dense material such as lead or DU
22 Activity New Unit Old Unit Becquerel 1 disintegration per second. CurieBased on number of disintegrations from 1 g of radium x 1010 dps.
23 Measure of the activity per unit mass or volume Specific ActivityMeasure of the activity per unit mass or volumeBq/g or Bq/ml
24 Half Life ( T1/2 )Time1 half life1 half life1 half life
25 Half Life Fluorine-18 110 min Phosphorus-32 14.3 d Iodine dSulphur dCobalt yTritium (Hydrogen-3) yCarbon y
26 Radiation DoseGray (Gy) – absorbed dose.Defined as 1 Joule of energy absorbed per kilogramme of material.Sievert (Sv)– Unit of equivalent dose and effective dose100 rad = 1 Gray ( 100 rem = 1 Sv) 1mrad = 10 µGray ( 1 mrem = 10 µSv)
27 Next…Short video:Working Safely with Radioactivity