atomic structure Flashcards
what is the atomic theory and who proposed it
the theory that everything is made up of tiny particles which cannot be broken down any further and are separated by empty space, proposed by democritus around 500 BC
what was john daltons theory on atomic structure
atoms are solid spheres and different types of spheres might make up the different elements
who came up with the plum pudding model
jj thomson
what was ernest rutherford’s experiment
directing alpha particles into a thin sheet of gold
what is the nuclear model
atoms are made up of a compact nucleus and are surrounded by a cloud of negative charge
what was the flaw in rutherford’s nuclear model
there was nothing stopping the cloud of negative charge from rushing into the nucleus meaning that the atom should just automatically collapse
how did niels bohr improve on the nuclear model
he said that there were electrons orbiting the nucleus which prevents the atom from collapsing
which two science discovered protons and neutrons
protons - rutherford
neutrons - chadwick
when can an electron jump into another shell
only when it has gained enough energy
- we say that the electron is ‘excited’
where does the energy required for an electrons to jump into a higher energy level come from
from electromagnetic radiation
what happens when an electron returns to its original, lower energy level
energy is released as electromagnetic radiation
what is ionisation
when one of the outermost electrons gains so much energy that it is able to completely leave the atom
- this leaves the atom with a positive charge
what is radioactive decay
when isotopes emit something so that they can become more stable
what are alpha particles made up of
2 protons and 2 neutrons
what are alpha particles made up of
2 protons and 2 neutrons
how penetrative are alpha particles
alpha particles are not very penetrative
- stopped in a few cm of air
- absorbed by a single sheet of paper
how penetrative are alpha particles
alpha particles are not very penetrative
- stopped in a few cm of air
- absorbed by a single sheet of paper
how ionising are alpha particles
they are very strong ionising due to their large size and strong charge
what are beta particles
just an electron
where to beta particles come from
- one of the atom’s neutrons decays into a proton and electron
- the proton stays in the nucleus while the electron is emitted out at high speed
how ionising are beta particles
moderately ionising due to their small size
how penetrative are beta particles
- stopped by several metres of air
- stopped by 5mm of aluminium
how penetrative are beta particles
- stopped by several metres of air
- stopped by 5mm of aluminium
what are gamma rays
waves of electromagnetic radiation
how ionising are gamma rays
they are weakly ionising as they pass through material easily
how penetrative are gamma rays
very penetrative
- can travel long distances in air
- stopped by thick sheets of lead
- stopped by multiple metres of concrete
what happens to the mass and atomic number when an alpha particle is emitted
mass number - 4
atomic number - 2
what happens to the mass and atomic number when beta radiation is emitted
mass number stays the same
atomic number + 1 (because it gains a neutron)
what is meant by the activity of the sample and what is it measured in
the overall rate of decay
- measure in becquerels (Bq)
what is meant by half-life
the time taken for the number of decays to halve
the time taken for the number of radioactive nuclei in a sample to halve
what device is used to find the activity of a radioactive material
geiger-muller tube and counter
what is irradiation
the process by which objects are exposed to radiation
what is contamination
when radioactive particles get onto other objects
what determines how harmful radiation is
- type of radiation
- where you’re exposed to it
- the amount of radiation you receive
why are ionising radiations dangerous
they can enter living cells and interact with the molecules inside
- ionises our DNA which can cause mutations (like cancer)
what is the most harmful type of radiation
alpha radiation as it is very ionising
what is the least harmful radiation
radio waves
what type of radiation is dangerous if it is coming from an external source
beta and gamma
how can we protect ourselves from irradiation and contamination
- wearing gloves and overalls
- using tongs to pick of radioactive material
- keeping the item in a lead lined box
how can radiation be used to help treat cancer
the radiation can help kill cancer cells however this will make the patient experience many side effects like hair loss and vomiting
- we call this radiotherapy
what are medical tracers
injecting a patient with radioactive material to track the movement of isotopes around the body by tracking the radiation they emit
what is nuclear fission
the splitting up of a large and unstable nuclei into smaller nuclei while also releasing large amounts of energy
what are the two ways nuclear fission can happen by
- spontaneously
- absorbing a neutron
what are the steps of nuclear fission
- fire a neutron into the nuclei
- this causes it to become unstable and then split into two daughter nuclei and a few neutrons ( + loads of energy)
- the daughter nuclei then repeat the process
what is the purpose of control rods
to be lowered into the nuclear reaction to absorb neutrons as this helps control the rate of nuclear fission
how is the energy from nuclear reactors used
the energy is used to heat up water to create steam, the steam then drives the turbines which are connected to a electricity generator
what are the pros of nuclear energy
- uranium and plutonium fuel is relatively cheap
- large and steady amount of energy
- doesn’t produce greenhouse gases
what are the pros of nuclear energy
- uranium and plutonium fuel is relatively cheap
- large and steady amount of energy
- doesn’t produce greenhouse gases
what are the cons of nuclear energy
- nuclear power plants are very expensive to build
- nuclear waste is expensive to get rid of
- risk of major disaster
what is nuclear fusion
when two lighter nuclei fuse to form a larger nuclei
what did nuclear fusion make/fuel
nuclear fusion is how all elements heavier than hydrogen were made and it is what fuels stars
