Radioactivity (10) Flashcards
At the centre of every atom is a _____________
Nucleus
The nucleus of an atom, contains __________ and ___________
Protons and neutrons
The nucleus of an atom makes up most of the _______ of the atom, but takes up virtually no __________
Weight Space
The electrons are _______________ charged and are really small
Negatively
The number of protons in the nucleus is called the ____________ number
Number of protons = atomic number
The total number of protons and neutrons in the nucleus is called the __________ number
Mass
What are isotopes
Atoms of the same element with different numbers of neutrons
Isotopes are atoms of the same __________ with different numbers of ___________
Element
Neutrons
This means that different isotopes have different __________ numbers
Mass numbers
Usually each element only has one or two ___________ isotopes
Stable
If the nucleus of an atom is unstable then it tends to be _____________. The unstable nucleus decays and emits _______________
Radioactive
Radiation
Radioactive decay is a ____________ process
Random
The nuclei of unstable isotopes break down at ___________. If you have 1000 unstable nuclei, you can’t say when any of one them is going to decay, and you can’t do anything at all to make a _________ happen
Random
Decay
Each nucleus decays spontaneously and is completely unaffected by physical conditions such as _________________ or ____________ bonding
Temperature
Chemical bonding
When a nucleus does decay it spits out one or more of the three types of radiation _________, ________ or __________
Alpha
Beta
Gamma
In the process of decay, the _________ often changes into a new element
Nucleus
There is (low level) background nuclear radiation all around us all the time which come from
Space
Substances on earth
Living things
Human activity (nuclear explosions)
Nuclear radiation causes ______________ by bashing into atoms and knocking _____________ off them. Atoms (with no overall _________) are turned into ______ (which are __________) - hence the term ionisation (being turned into ions)
Ionisation
Electrons
Charge
Ions
Charged
The further the radiation can penetrate before hitting an atom and getting stopped the _________ damage it will do along the way and so t?’‘he _________ ionising it is
Less Less
____________ radiation can be detected with a Geiger-Muller detector
Ionising
Alpha particles are made up of ___ protons and ___ neutrons
2 protons and 2 neutrons
What are the features of an alpha particle
Big, heavy, slow moving
What are the features of a beta particle
Quite fast, quite small
What are the features of a gamma particle
No mass - just energy
___________ are big and heavy so they don’t _______________ far into materials and are stopped quickly
Alpha
Penetrate
Because of their size, alpha particles are strongly ______________ which means they bash into a lot atoms and knock ______________ off them before they slow down, which creates lots of _______
Ionising
Electrons
Ions
Because they’re electrically charged, ________ particles are deflected by electric and ____________ fields
Alpha
Magnetic
How does emitting an alpha particle change the mass and atomic numbers of an atom
The mass number decreases by 4 and the atomic number decreases by 2.
A beta particle is an ____________ which has been emitted from the nucleus of an atom when a __________ turns into a proton and an electron
Electron
Neutron
When a beta particle is emitted, the number of ___________ increases by 1. So the __________ number increases by 1 but the _______ number stays the same because a neutrons is lost when it turns to a proton. (The mass number stays the same because the neutron is replaced by a proton). (E.g. instead of their being 6 protons and 6 neutrons, there are now 7 protons and 5 neutrons - still 12 overall but proton number is higher)
Protons
Atomic
Mass
Beta particles penetrate moderately before colliding and are moderately ________________ too
Ionising
Because beta particles are (negatively) ___________ they are deflected by electric and magnetic fields
Charged
___________ particles can penetrate a long way into materials without being stopped
Gamma
Gamma rays are ___________ ionising because they tend to pass through rather than collide with _________. But eventually they hit something and do damage
Weakly
Atoms
Gamma rays have no __________, so they’re not deflected by electric or magnetic fields
Charge
________ emission always happens after alpha or beta ________ . You never get just gamma rays emitted.
Gamma Decay
What blocks alpha particles
Paper
Skin
A few centimetres of air
What blocks beta particles
A thin sheet of metal
What blocks gamma rays
Thick lead
Very thick concrete
An alpha particle is made up of 2 protons and 2 neutrons and has a ____________ charge
Positive
A beta particle is an electron and so has a _____________ charge
Negative
A gamma ray is a wave which has _____ charge
No charge
What is half-life
The time it takes for a radioactive material to lose half of its radioactivity / for half of the radioactive atoms present to decay
The faster an alpha particle is travelling the _______ it will be deflected by a nucleus
Less
The more positively charged a nucleus is (i.e the higher the atomic number) the ________ an alpha particle will be deflected
More
The closer an alpha particle particle passes to the nucleus the ___________ it will be deflected
More
Most to least dangerous radiation outside the body
Gamma (most)
Beta
Alpha (least)
Most to least dangerous type of radiation inside the body
Alpha (most)
Beta
Gamma (least)
Fastest to slowest type of radiation
Gamma (fastest - speed of light)
Beta
Alpha (slowest)
Highest to lowest range of radiation in air
Gamma (most)
Beta (up to a meter)
Alpha (least)
Which types of radiation are affected by a magnetic field
Alpha and Beta
Most to least ionising type of radiation
Alpha (most ionising)
Beta
Gamma (least)
Charge of alpha radiation
+2
Charge of beta radiation
-1
Charge of gamma radiation
0
Mass of alpha radiation
4
Mass of beta radiation
1/2000
Mass of gamma radiation
0
Most to least penetrating
Gamma (most)
Beta
Alpha (least)
What is alpha radiation stopped by
Thin sheet of paper
What is beta radiation stopped by
Thin sheet of metal
What is gamma radiation stopped by
Thick sheet of lead
How does alpha decay affect the element
It turns into a new element, 4 off the top number 2 off the bottom number + a helium particle with 4 as the top number and 2 as the bottom number
How does beta decay affect the element
It turns into a new element top number stays the same an extra 1 onto the bottom number + an electron with 0 as the top number and -1 as the bottom
How does gamma decay affect radiation
It doesn’t
Sources of background radiation:
Rocks
Air (radon)
Space
Building materials
What is ionisation
The adding or removing of electrons from an atom leaving the atom charged
What is half life
The average time it takes for half of the radioactive nuclei to decay. E.g if something has lost 50% of its Carbon 14 then it will be 5700 years old
Radioactivity is a __________ process - we can’t predict which atom will __________ when
Random
Decay
Carbon dating is a useful way of finding the age of living things that have carbon ____ in them
Carbon 14
Carbon dating is not useful for materials that are more than _________ years old or less than ______ years young
50000 years old 200 years young
Explain how a smoke detector works
Due to alpha particles inside the smoke detector a small current is formed between 2 plates (positive and negative) When smoke gets in the way, the current stops and this triggers the alarm
Explain how radiation is used to measure the thickness of paper
Above the paper is beta radiation Below the paper is a detector If the detector detects too much beta then the paper is too thin If the detector detects too little beta then the paper is too thick If the detector detects that the paper is the wrong thickness then a message will be sent and the pressure applied to the paper will be altered
Why is gamma radiation harmless in the body
Because it is so not ionising that it doesn’t affect any of the body cells
Nuclear power stations use nuclear ___________
Nuclear fission
What is nuclear fission
The splitting of an atom, which releases energy
In a nuclear reactor, nuclear fission is carried out in a _____________ chain reaction
Controlled
How does a nuclear reaction work
If a slow-moving neutron gets absorbed by a uranium-235 nucleus, the nucleus can split. When it splits it releases a small number of neutrons which can go on to hit more uranium-235 nuclei which then splits and splits more and the reaction goes on and on
When uranium-235 splits in 2 it will form ____ new daughter nuclei
2
The new nuclei formed from nuclear fission is usually _________________ because they have the ‘wrong’ number of neutrons in them. This can cause huge amounts of radioactive ___________
Radioactive
Waste
How does a nuclear reactor work
Free neutrons in the reactor start the process The reaction begins thus the temperature rises The moderator (often water) slows neutrons so that the collisions are successful Control rods absorb some neutrons to keep it controlled A gas (CO2) is pumped in to take away the heat The gas is then passes through a heat exchanger where it gives its energy to water which is then heated and turned into steam. This steam turns a turbine which turns a generator, generating electricity
How a nuclear reactor works: Free neutrons in the reactor start the process The reaction begins meaning that the temperature __________ The moderator (often ________) slows neutrons so that the collisions are successful Control rods __________ some neutrons to keep it controlled A gas (CO2) is pumped in to take away the _________ The gas is then passes through a heat exchanger where it gives its energy to _________ which is then heated and turned into steam which turns a ___________ which turns a ___________, generating ______________
Rises
Water
Absorb
Heat
Water
Turbine
Generator
Electricity
Nuclear fission equation:
Neutron -> Uranium which then splits in 3 - (krypton, barium and energy) this energy comes with 3 more neutrons
How is a uranium-235 nucleus made to undergo fission
By surrounding it with neutrons meaning that it absorbs one
Give one peaceful use of nuclear fission
Generating electricity
