Radioactivity and particles Flashcards
Protons
Charge= +1 Mass= 1
Electrons
Charge= -1 Mass= 0
Neutron
Charge= 0 Mass = 1
Mass and atomic
top number = mass
bottom num = atomic
What is the mass number
Number of protons and neutrons
What is the atomic number?
Number of protons
Plum pudding model
Thompson suggested that atoms were spheres of positive charge with tiny negative electrons stuck in them
What was the alpha scattering experiment?
scientists in rutherfords lab tried firing a beam of aplha particles at thin gold foil. Plum pudding theory expected the particles to pass through the gold sheet. Although some did, some were deflected more than they expected. Some were deflected back the same way they had come
What did the alpha scattering experiment reveal?
Most of the mass of the atom was concentrated at the centre in a tiny nucleus which has a positive charge
lol
number of protons equals number of electrons
What are isotopes?
Atoms which have the same number of protons and a different number of neutrons
Alpha radiation
Alpha Particles- helium nuclei 2 neutrons and 2 protons Radiation- particle emitted from nucleus Don't penetrate far, only can travel a few cm in air and absorbed by a sheet of paper Strongly ionising
Beta particles
A fast moving electron released by nucleus.
No mass and charge of -1
Moderately ionising
Moderately penetrating, absorbed by a sheet of aluminium
Why are beta emitters used to test the thickness of sheets of metals?
Because the particles are not immediately absorbed by the material like alpha radiation and do not penetrate as far as gamma rays. Therefore slight variations in thickness affect the amount of radiation passing through the sheet
Gamma rays
EM waves
stronly penetrating
weakly ionising
absorbed by thick sheets of lead or metres of concrete
Alpha decay
It decreases the charge and mass of the nucleus. loses 2 protons and 2 neutrons
Beta decay
It increases the charge of the nucleus. Mass number remains same proton decreases by 1
Whats’s a half life?
Time taken for the number of radioactive nuclei in an isotope to halve
How to work out half life from a graph
read the initial activity on the y axis. This is activity when time=0
divide by 2
read off time from x axis
What is a nuclear fission power plant
A neutron is fired into a uranium-235 nucleus. It becomes unstable and splits into two smaller nuclei and releases 2 or 3 more neutrons
How can nuclear fission lead to a chain reaction?
2 more neutrons are released which are reflected by the u235 which undergo fission
What is the shield?
concrete absorbs radiation
What is the control rod
Boron, absorbs neutrons to slow fission reactants, the higher rectangle
What is the fuel rod?
Uranium contains radioactive material for fission, Fatter rectangle
What is the moderaotr?
graphite, slows the nutrons down so fission can continue
What is nuclear fusion
2 nuclei have to overcome the electrostatic force between them and get close enough for the strong force to hold them together, Converts mass into energy.
What is nuclear fission?
type of nuclear reaction that is used to release energy from large and unstable atoms by splitting them into smaller atoms
