The atom and radioactivity Flashcards
history of theories on structure of atom
Democritus: all matter made up of identical lumps, couldn’t be broken down
John Dalton: each element made up of different type of atom
Thomson: plum pudding theory (sphere of positive charge with negative electrons scattered in it)
Rutherford: mostly empty space, positive charge concentrated at centre of nucleus
Rutherford experiment
fired alpha particles at thin sheet of gold
most went through
some bounced right back
nuclide definition
atoms comprised of particles number of proton and neutrons
ionisation definition
when atom/molecule loses electrons
forms ions
ionising radiation
high-energy radiation able to cause atoms/molecules to lose electrons
EM spectrum able to cause ionisation
UV
X-rays
gamma rays
radioactive meaning
decay and give out ionising radiation to become more stable
nature of different types of radiation
alpha = 2 protons, 2 neutrons beta = electron gamma = EM wave
charge of different types of radiation
alpha = 2+ beta = -1 gamma = 0
mass of different types of radiation
alpha = He nucleus (relatively large) beta = very small (negligible) gamma = zero
range of different types of radiation
alpha = 3-5cm beta = 2-3m gamma = 100s of metres
ionising effect of different types of radiation
alpha = very strong due to size beta = moderately ionising gamma = very weak, tends to pass through rather than interact with particles
penetration of different types of radiation
alpha = slow moving, stopped by paper, skin beta = moderate, blocked by thin plate of metal gamma = high, blocked by thick metal plates
different types of radiation in magnetic/electric field
alpha: larger charge + feels greater force in these fields+ deflected less due to greater mass than beta, deflected in opposite direction to beta
beta: deflected in opposite direction to alpha (opposite charge)
gamma: doesn’t get deflected (no charge)
danger of different types of radiation
alpha: most dangerous inside of body due to low penetration power
beta + gamma most dangerous outside due to higher penetration power
why emitting gamma rays doesn’t change element of nucleus
gamma ray is just energy
alpha decay
atomic number -2
mass number -4
beta decay
atomic number +1
mass number 0
neutron turns into proton + electron, electron emitted