Atomic structure Flashcards
how do electrons jump up energy levels
they become excited from the energy they get from em radiation
how is em radiation emitted in an atom
when an excited atom falls back down to a lower energy level emitting the energy as em radiation
the mass number is……….
the atomic number is………..
the mass number is the protons+neutrons and is at the top
the atomic number is the number of protons and is at the bottom
what is ionisation
Electrons can also absorb enough energy to leave the atom altogether, this is known as ionisation
what do unstable isotopes do
radioactive decay where they emit something to become more stable
what are the 4 types of nuclear radiation
alpha
beta
gamma
neutrons
what are alpha particles made up of and what is this the same as
2 protons and 2 neutrons same as nucleus of a helium atom
what are the properties of alpha particles
large
have 2+ charge
least penetrative-stopped by few cm in air or single sheet of paper
-heavily/most ionising
what does ionising mean
how easily something knocks off electrons off atoms it collides with
what is the charge of beta particles
-electrons
-charge of -1 with little mass
what are the properties of beta
-small
-moderately ionising and penetrative(stopped by several m of air /5mm of aluminium to stop
how are beta particles formed
neutron decays to a proton and electron which gets emitted at high speed
what are gamma rays and how are they emitted
not particles but em waves that are emitted after alpha and beta radiation as a way of releasing energy
what are the properties of gamma rays
-they have no mass or charge so highly penetrative(stopped by thick sheets of lead or multiple m of concrete to stop)
-weakly ionising
how are neutrons emitted
if a neutron is making a nucleus unstable it throws out the neutron to make it more stable
what is the equation for alpha decay
loses 4 to the mass number and 2 atomic number
what is the equation for beta decay
0 to the mass number +1 to the atomic number
what is the equation for neutron emission
+1 to the mass number
what is the activity
overall rate of decay of all the isotopes in our sample
measured in bq where 1 bq =1 decay per second
what is half life
time taken for no of decays(activity)to half
what is the count rate
the no of decays counted by a geiger muller counter
what is irradiation
when objects are exposed to any type of radiation
what is contamination
when radioactive particles get onto other objects
what is the harm of contamination
the radioactive material you are contaminated with is likely to decay and irradiate you
why is ionising radiation most dangerous
can enter living cells and interact with molecules inside
this involves dna which they can ionise and cause genetic mutation
in rare cases can cause cancer
what 3 things affect dosage
-distance from the source
-how radioactive the material is
-how long you are exposed to it
how do we minimise irradiation and avoid contamination when we are around radioactive source
precautions like
-wearing protective gear like gloves and overalls
-handling item with tongs or tools
-keeping item in lead lined box
what is the only way you can spread radiation
by holding a radioactive source
what causes radiation sickness and what symptoms does it have
recieving large doses of radiation across the entire body which will cause vomiting tiredness or hair less making you ill as most of your cells are killed or damaged
how can radiation treat cancer and what is this called
can be used by doctors to destroy can cer cells
called radiotherapy
what are the 2 ways in radiotherapy that the radioactive source is delivered
externally or internally
what is the difference between external and internal radiation
-external is performed by emitting gamma rays targetted at cancer site at different angles so it gets the highest dose
-internal is performed with beta where it is placed next to or inside cancer
what are the side effects of radiotherapy
kills other healthy cells in the body causing patients to feel sick
how are medical tracers used
placing certain radioactive isotopes in a body by injection or swallowing by tracking the radiation they emit to see if certain organs are working by absorbing they right amount
how do we minimise risk in treatments
use low dose with a short half life
what is nuclear fission
splitting of unstable large nuclei into smaller nuclei and lots of energy
what are the 2 ways nuclear fission can occur
-spontaneously-happens on its own(rare)
-absorbing a neutron-makes nucleus less stable
what are the steps of nuclear fission
1)fire slow moving neutron at unstable nuclei
2)it becomes less stable splitting apart into 2 daughter nuclei
2 or 3 neutrons
and lots of energy in form of gamma radiation
how does fission cause a chain reaction
the neutrons emitted can react with another unstable nuclei releasing huge amounts of energy(eg a nuclear bomb)-uncontrolled
what are control rods and what role do they play in fission
control rate of fission which are lowered into reactor to absorb neutrons slowing down rate of reaction
what is the energy from fission used for
heat up water turn it to steam drive turbines connected to an electricity generator
what is nuclear fusion
when 2 light nuclei fuse to form single large nuclei and a lot of energy
what has nuclear fusion done
fuels stars
formed all elements heavier than hydrogen
why is so much energy released in nuclear fission
some mass of original nuclei is transferred to energy as em radiation instead of new nucleus
what are the pros/cons of nuclear fusion
pros
no radioactive waste
easily make the hydrogen needed as fuel
cons
-extremely high pressures and temperatures needed
-cant be done on earth
what are differences between fission and fusion
fusion-only happens inside stars
fission-much less energy produced
what is fusion inside stars
hydrogen fusing to become helium nuclei
Why does fusion only happen at very high temperatures and pressures?
To overcome the repulsion of the positively charged nuclei
