P7 Flashcards
How did the alpha scattering experiement help develop the nuclear model?
Alpha particles that deflcted back - means most of the mass of the atom is concentrated at the centre in a nucleus
Alpha particles that passed straight through - meant most of the atom is empty space
What are isotpes?
Atoms with the same number of protons but a different number of neutrons
What are properties of alpha radiation/particles?
Like a helium atom
They dont penetrate far, stopped quickly
They only travel a few cm in air, get absorbed by a sheet of paper.
Strong ionisation
What are properties of beta particles?
They are just a fast movimg electron
Have a charge of -1, no mass
Moderatly ionising
They penetrate Moderatly into materials
Travel A few metres in air
Absorbed by a sheet of aluminium
What are properties of gamma particles?
They are electromangnetic waves
They penetrate far into materials
Travel long distances through air
Weak ionisation
They can be absorbed by thick sheets of lead or concrete
When alpha particles undergo radioactive decay what changes?
Protons is reduced by 2, mass number is reduced by 4
When beta particles undergo radioactive decay what changes?
Proton increases by 1
When gamma particles undergo radioactive decay what changes?
No change
Why do unstable nuclei gove out radiation?
They undergo decay to become more stable
Define the activity of an unstable nucleus?
Activity is the rate of decay of a unstable nuclei
What is the unit pf radioactive activity?
Becquerel(Bq)
What is count-rate?
Number of radioactive decays per second for a radioactive source
Describe the nature of radioactive decay?
Random
Impossible to predict which nuclei will decay and when
What is irradation?
Process of exposing a material to nuclear radiation
Material does not become radioactive
Why are isotopes with long half lives particularly harmful?
They remain radioactive for much longer
They must be stored carefully to avoid radiation exposure
