Radioactivity

• 1/10000 alpha particles deflected back when fired at a gold nucleus
• Most alpha particles passed straight through which showed the atom was mainly empty space
• The N-Z curve curves above the line N=Z
• $\beta-$decay occurs to the left of the N-Z line
• $\beta+$decay occurs to the right of the N-Z line
• Alpha decay occurs above the N-Z line
• Activity is the rate of decay of a radioactive source
• The decay constant is the probability of decay in a nucleus
• Half life is the average time taken for the activity of a sample to halve
• The inverse square law states that intensity is inversely proportional to the square of the distance
• The nuclear density of an atom is constant
• The N-Z graph stops being directly proportional at (20,20)
• density of a nucleus is much bigger than the density of an atom
• theory of closest approach uses the Rutherford scattering experiment to estimate the size of the nuclear radius
• when the alpha particles have a kinetic energy and potential energy of 0, they are as close as they can get to the gold particle and so r is an estimate of the radius
• the closest approach theory will always be an overestimate
• closest approach is an estimate of radius but electron scattering is a measurement
• coloumb equation for closest approach = $\frac{Qq}{4\pi\epsilon or}$
• a larger nucleon number means a larger nucleus
• nuclear density can be calculated by substituting into p=m/v
• atomic density equation only includes constants so does not depend on size of atom
• the first minimum of the intensity angle graph created by the electron diffraction will be the nuclear radius
• a higher decay constant means a faster rate of decay
• half life and decay constant are inversely proportional
• technetium-99m is used for medical diagnosis
• technetium-99m is good for medical imaging because

  • it has a short half life (6hrs)
  • it is a pure gamma emitter
  • It can be prepared on site