P1P6 - Radioactivity Flashcards
What is the charge and mass of a proton?
C - +1
M - 1
What is the charge and mass of an electron?
C - -1
M - 1/1835
What is the charge and mass of a neutron?
C - 0
M - 1
What did JJ Thompson discover?
He discovered that there was a positive mass with negative electrons running throughout.
Who made the Plum pudding model and in what year?
J.J Thompson
1897
What did Ernest Rutherford discover?
Ernest Rutherford discovered that alpha particles could bounce back off atoms.
He found that an atom’s mass is concentrated in its centre. This was called the “nucleus” and it has positively charged protons.
Who made the nuclear model and in what year?
Ernest Rutherford
1909
What did Neils Bohr and James Chadwick discover?
Neils Bohr discovered that electrons orbit the nucleus at fixed distances.
In 1932, James Chadwick discovered that some particles in the nucleus have no charge at all. He called them neutrons.
Who made the modern model and in what year?
Neils Bohr and James Chadwick
JC 1932
What happens when an atom emits radiation?
When atoms emit electromagnetic radiation, electrons can drop to a lower energy level, emitting visible light at a particular wavelength.
What happens when an atom absorbs radiation?
When atoms absorb electromagnetic radiation, electrons move to a higher energy level.
What did Rutherford use in his experiment?
Thin gold foil
Alpha particles
What does the number of protons define?
Defines the element.
What is the nucleon number?
he nucleon number is the total number of protons and neutrons in a nucleus.
What is the label for proton number?
Z
What is the label for nucleon number?
A
What happens when an atom gains or loses charge?
When an atom becomes charged by gaining or losing electrons it becomes an ion.
Why are atoms neutral?
Equal numbers of electrons and protons.
What are ions?
Charged particles.
What is an isotope?
An element with the same amount of protons but different amount of neutrons.
What are the 3 isotopes of hydrogen?
Protium
Deuterium
Tritium
How many neutrons do all 3 isotopes of hydrogen have?
Protium - 1 neutron (Most common)
Deuterium - 2 neutrons
Tritium - 3 neutrons
What is protium used in?
It is used in hydrogen fuel cells and the production of plastics.
What is deuterium used in?
Nuclear fusion.
What is tritium used in?
Thermonuclear fusion weapons.
What is a nuclide?
A type of isotope.
Nuclide refers to a specific nucleus that contains a certain number of protons and neutrons.
Why can an atom become unstable?
When the atoms of an element have extra neutrons or protons it creates extra energy in the nucleus.
How can an unstable nucleus become stable over time and what is it called?
By slowly emitting ionising radiation randomly over time. This os called radioactive decay.
What are the 3 types of ionising radiation?
Alpha
Beta
Gamma
What happens in Beta Minus decay?
In beta-minus decay, a neutron decays to form a proton and electron.
This electron is then ejected (kicked out) of the nucleus.
What happens in Beta Positive decay?
Beta-plus decay
In beta-plus decay, a proton decays to form a neutron and a positron.
The positron is then ejected (kicked out) of the nucleus.
What happens in Alpha radiation?
Produced by alpha decay.
Releases helium nuclei, also known as alpha particles.
Results in the mass of the nucleus decreasing by 4 atomic units (2 protons and 2 neutrons).
What is an alpha particle also called?
Helium nuclei
How is Alpha decay represented?
- Mass decreases by 4
- Atomic number decreases by 2
How is Beta - decay represented?
- Mass number stays the same
- Atomic number increases by 1
How is Beta + decay represented?
- Mass stays the same
- Atomic number decreases by 1
Which decay is the most ionising, partially and least ionising?
Alpha - Most
Beta - Partially
Gamma - Lease
Which decay is the most penetrating, partially and least penetrating?
Alpha - Least
Beta - Partially
Gamma - Most
What are the decays stopped by?
Alpha - Paper
Beta - Aluminium
Gamma - Thick Lead
What are the three ways in detecting radioactivity?
Cloud chamber
Photographic film
Geiger counter
How does a cloud chamber detect radioactivity?
A cloud chamber is a container full of air containing alcohol vapour.
Ionising radiation enters the air and leaves a trail of ionised air molecules.
The alcohol vapour condenses on the ionised air molecules, showing the trail of radiation.
How does a photographic film detect radioactivity?
Ionising radiation has the same effect on photographic film as light.
A bright spot appears wherever the ionising radiation hits the film.
How does a Geiger counter detect radioactivity?
Ionising radiation enters a tube full of low pressure gases.
It ionises the atoms in the gas, knocking electrons out of the atoms.
The gas can now conduct electricity and completes an electric circuit.
Current flows between electrodes.
The current produces a clicking noise.
The count-rate is the number of decays recorded each second.
What are Beta particles?
Electrons
What does Beta+ emit and Beta- emit?
Beta+ - Positron
Beta- - Electron
What is the relative mass of an alpha particle?
4
Whats the difference between ionising and penetrating?
More strongly ionising radiation does more damage, but doesn’t go far.
While penetrating radiation goes further, but does less damage.
How does organs get explored with gamma radiation?
If we put a gamma-emitting isotope into a patient’s body, we can trace (follow) the radiation’s movement around the body.
Gamma radiation is the most penetrating type of radiation. This means it can pass through objects more easily than alpha or beta radiation.
This means gamma can leave the body without creating too much damage (ionisation).
Gamma radiation also has a short half-life. This means that the radiation vanishes quickly.
How does a smoke detector work?
A radioactive material fires alpha particles at a smoke detector.
If there is smoke between the radioactive material and the smoke detector, then fewer alpha particles will reach the detector.
This will set off the smoke alarm.
What happens in nuclear fission fully explained?
A neutron collides with a large nucleus and is absorbed. This creates an unstable nucleus.
This nucleus then splits into fragments. This releases large amounts of energy and more neutrons.
These neutrons can then collide with other nuclei.
Nuclear fission splits 1 nucleus into 2 or more smaller nuclei.
What is nuclear fission?
A neutron collides with a large nucleus and it splits 1 nucleus into 2 or more smaller nuclei.
Why does nuclear fission produce a chain reaction and how is it controlled?
The neutrons released by one reaction cause another reaction to occur.
Control rods and moderators are used to control the reactions taking place.
What atoms are used in nuclear fission?
Uranium-235
Plutonium-239
What do control rods control in a nuclear reactor?
Number of neutrons in the reactor.
What do moderators control in a nuclear reactor?
They control the speed at which the neutrons are travelling in the reactor.
What happens if nuclear fission isn’t controlled?
Radioactive explosion.
What is nuclear fusion?
Nuclear fusion fuses 2 smaller nuclei to create 1 larger nucleus. Creating this larger nucleus releases energy.
What are the conditions needed for nuclear fusion?
For two protons to fuse, they must have enough energy to collide and overcome their electrostatic repulsion.
Therefore fusion requires a very high temperature and pressure.
What is the name of the layer of O3 molecules which block harmful, ionising radiation from the Sun?
Ozone layer
What is half life?
The time taken for half the unstable nuclei in a sample of radioactive isotope to decay.
What are some safety precautions for radioactive substances?
Shielding
Rubber gloves
Lead-lined box storage
Can ionising radiation cause cancer?
Yes
What are pros and cons of radiotherapy?
Cons - May kill healthy cells, which can lead to radiation sickness
Pros - Can kill mutated cancer cells, which lead to healthy and longer life.
Why would we use radiation with a long half life in medical treatment?
To track its path through the body over time.
What is radioactive contamination?
Contamination is when radioactive substances occur from inside something.
What is radioactive irradiation?
Irradiation is when something is exposed to radiation on its outside.
Why is alpha most harmful in our bodies than Beta and gamma?
Alpha is the most dangerous form of radiation inside the body.
It cannot penetrate the skin and so stays in the body.
Beta and alpha can just pass out the body.
