P6 | radioactivity Flashcards
why is alpha radiation highly ionising? why is it dangerous if inhaled?
they have a 2+ charge (helium nucleus has 2 protons) meaning they can ionise very easily
they can easily damage/ionise our cells
why is alpha radiation lowly penetrative?
they have 2 protons meaning they are heavy, meaning they lose their energy very quickly in air and can’t travel far
why is gamma radiation lowly ionising?
they have no charge meaning they are very weak ionisers
why is gamma radiation very penetrative?
gamma radiation is energy; high energy and high frequency travelling at the speed of light, making them very penetrative and able to travel very far
which part of a power station provides thermal energy from a chain reaction?
nuclear reactor
which part of a power station transfers kinetic energy into electrical energy?
generator
how do control rods reduce the number of nuclear reactions in a reactor?
- control rods can be moved in and out
- absorb excess neutrons
- meaning fewer neutrons left to cause fission
why is nuclear fusion important to life on earth?
nuclear fusion occurs in the sun which provides energy needed for life on earth
how do moderators control the nuclear reactions in a reactor?
moderators slow down neutrons in order for them to be absorbed by/collide with unstable nuclei
how can the thermal energy released by fission/fusion be converted into electrical energy in a power station?
- thermal energy is used to boil water to create steam
- this steam is used to drive the turbine
- the turbine is used to turn the generator
what is radioactive decay?
the random, spontaneous breakdown of an unstable nucleus resulting in the release of energy and matter from the nucleus
what is background radiation?
radiation that is always present
sources of background radiation
- medical sources
- food and drink
- gamma rays from rocks
- radon gas from ground
- nuclear power and testing
- cosmic rays
why is radon gas dangerous and how can it be removed?
- colourless and odourless
- when inhaled, alpha radiation from radon can damage cells which can cause cancer
- can be prevented by installing pumps into buildings to remove the gas
what is cosmic (microwave) background radiation?
radiation from space that is always present; produced during the Big Bang; leftover energy from the initial explosion
describe how a teacher should use a Geiger-Müller (GM) tube to compare the count-rates from two different radioactive rocks
- put rocks near/in front of the GM tube
- measure the count rates separately for each rock for the same time period
- keep the distance between the GM tube and rock the same for both rocks
- take background radiation into account
- repeats the readings and take averages
how were electrons distributed in the plum pudding model?
electrons are randomly distributed in a sphere of positive charge
what did the gold foil experiment conclude?
a majority of alpha particles went straight through = most of an atom is empty space
some alpha particles deflected slightly = atoms have a positively charged nucleus which repels positive alpha particles
very few alpha particles completely deflected/did not pass through = the nucleus (mass) is very small and in the centre of the atom
why was the plum pudding model scrapped?
the new experimental evidence from the gold foil experiment didn’t support the plum pudding model
the plum pudding model could not explain why some alpha particles were deflected backwards
what was Bohr’s nuclear model?
- a tiny central positively charged nucleus in the center which contains most of the atom’s mass
- most of the atom is empty space
- electrons are in fixed orbits called energy levels/electron shells
process of beta minus decay
- a neutron becomes a proton and an electron
- mass number doesn’t change because even though a neutron has been lost, a proton has been gained
- atomic number increases by one because a proton is gained
process of beta plus decay
- a proton becomes a neutron and a positron
- mass number doesn’t change because a neutron is gained
- atomic number decreases by one because a proton has been lost
radiations
α⁴₂ = alpha
β⁰₋₁ = beta minus
β⁰₁ = beta plus / positron
γ⁰₀ = gamma
