What did Rutherford do?
Published results of his gold leaf experiment discovering a nucleus.
What did J.J tompson do?
Created the plum pudding model and was the first scientist to prove atoms are made of electrons with cathode rays.
What did Bohr do?
Proposed electrons were arranged in shells so they didn’t get attracted to the nucleus in the middle.
What did James Chadwick do?
Explained gamma radiation by a neutral particle.
What causes background radiation?
- Nuclear bombs
- nuclear powerstations
- sunlight-cosmic rays
What types of particles are given of through radiation?
What materials stop Alpha particles?
Thin materials like paper and skin.
also a few centimetres of air would stop it.
What materials stop gamma particles/rays
What can stop beta particles?
A thin sheet of aluminium.
What is an isotope?
An element with the same number of protons but a different number of neutrons.
What is half life?
The time taken for the number of nuclei in the radioactive isotope in a sample to halve
the time taken for it radioactivity to half.
What does the atomic number tell you?
The number of protons and in a neutral atom, the number of electrons.
What does the mass number tell you?
The number of protons + neutrons.
What are gamma rays used for?
- Killing bacteria by irritation,
- Diagnosing medical conditions by injecting a radioactive tracer that gets taken in by particular organs,
- external radiotherapy where beams of gamma rays(or x rays or protons) are directed at tumours. The surrounding tissues are protected by several low strength beams
- detecting leaks with tracers- absorbed into the earth around the leak and emits more radiation.A Geiger muller tube is used to detect the leak.
What can Beta particles be used for?
- Measuring the thickness of things like paper. Beta particles are fired through lets say paper and if more particles are getting through then it is thinner, if less particles are getting through then it is too thin.
- Used in internal radiotherapy when a Beta emitter is placed near the tumour and as they are more susceptible to radiation than normal, the tumour cells get killed.
How do smoke alarms work?
A source of alpha particles and an air gap is in the alarm. When the alpha particles are emitted, ionise with the air particles. These particles are attracted to oppositely charged plates creating an electric current. If smoke is there then the current will break setting of the alarm.
What is nuclear fission?
A slow moving neutron collides with uranium 235 and forms two isotopes. As it is very unstable, when it absorbs a neutron, it split into two daughter nuclei, 2 or more neutrons, gamma radiation and a lot of energy
What is nuclear fusion?
Two atomic nuclei join together to form a large nucleus and a lot of energy is released. However, you need a high temperature for this to happen as there is strong electrostatic repulsion and repel the atoms unless they have a lot of energy and are travelling very fast. This temperature only naturally occurs on a star/sun.
What is activity?
amount of radiation per second measured by a Geiger counter
What is alpha decay?
When a alpha particle is emitted due to an unstable nucleus (or more than 83 protons) causing the number of protons and the number of neutrons to go down by two. This means the mass number goes down by 4
What is radioactive decay?
The nuclei of some isotopes are unstable. They can split up or ‘decay’ and release radiation. Such isotopes are called radioactive isotopes or radioisotopes. When a radioactive isotope decays, it forms a different atom with a different number of protons.
What is beta(-) decay?
In Beta (β-) decay, a neutron changes into a proton plus an electron. The proton stays in the nucleus and the electron leaves the atom with high energy, and we call it a beta particle.
What is beta(+) decay?
occurs when radioisotopes have too many neutrons, β+ decay occurs when they have too many protons. In this case, a proton is converted into a neutron and a positive beta particle of β+. This is called a positron and has the same mass as an electron but the opposite charge (positive).
What is activity?
The amount of radiation present (measured by a Geiger counter)
What is intensity?
The energy emitted per meter squared every second
What are the dangers of gamma rays and x-rays?
They can cause mutations to the DNA in the cells of your body. This can kill the cells or cause cancer.
What are the uses of Gamma rays?
- sterilise food and medical equipment
- in scanners to detect cancer
- to treat cancer
What are the uses of x-rays?
- Medical uses, to scan your bones for damage
- in airport to see inside peoples luggage
What are the dangers of Ultraviolet rays?
UV in sunlight can damage your skin causing sunburn or over time can cause skin cancer
-damage your eyes
What are the uses of Ultraviolet rays?
- fluorescent lamps
- to detect forged bank notes with the watermarks which glow in UV light
- disinfect water
What are the uses of infrared radiation?
- in cooking (grills and toasters)
- thermal imaging
- remote controls
- security systems
What are the dangers of infrared radiation?
-too much can burn your skin
What are the uses of microwaves?
- satellite transmissions
What are the uses of radio waves?
- broadcasting TV and radio
- communication with ships, panes and satellites
What is nuclear radiation?
when energy is emitted from the nuclei of unstable atoms.
How do elections move between different energy levels?
Electrons can move between different energy levels in the atom if they absorb or emit electro magnetic radiation. When they absorb electromagnetic radiation they move up energy levels and when they emit electromagnetic radiation they move down energy levels.
What is the process called by which large amounts of energy is released to heat water in power stations?
What is a chain reaction?
In nuclear fission, when uranium 235 absorbs a neutron, it absorbs a neutron, it releases several more neutrons which then go and cause other uranium particles to decay, creating a chain reaction.
What is a controlled chain reaction?
When a chain reaction controlled using a different material along side the uranium atoms so that only one of the released neutrons can cause fission, hence slowing doing the reaction as their are fewer neutrons to cause the nuclei to undergo fission
Why can nuclear fusion not occur on earth easily?
Because the two nuclei need to be very close for fusion to occur and as they both have positive charges, they have very strong electrostatic repulsion meaning that extreme pressure and temperature is required to overcome this, usually only found in stars.
Explain the difference between nuclear fission and fusion
In nuclear fusion hydrogen nuclei fuse to produce a bigger helium nuclei.
Whereas in nuclear fission, uranium 235 splits in d two daughter nuclei and 2+ neutrons.
Fusion requires very high temperatures and fast moving hydrogen nuclei whereas fission requires a slow moving neutron to be absorbed. Both release lots of energy
How do neon signs work?
Gases on the inside absorbs energy (though electricity) causing the electrons to move up an energy level. They then need to move down to a more stable energy level by emitting light. They emit the colour which has the same amount of energy they absorbed in the first place.
What is the equation to work out activity?
number of nuclei that decay / time in seconds
How can ionising radiation be damaging?
Ionising radiation can break molecules into smaller fragments. These charged particles are called ions. Ions can then take part in other chemical reactions in the living cells. As a result, ionising radiation damages substances and materials, including those in the cells of living things. The ions themselves can take part in chemical reactions, spreading the damage. This may result in the living cells dying or becoming cancerous. Radiation can also affect DNA, causing mutations.
How do nuclear power stations work?
Fuel rods heat a coolant when a neutron is fired into the uranium causing nuclear fission to release lots of energy and heat the coolant. This coolant then turns water to steam, turning a turbine etc.
What happens to the mass and charge of the nucleus when alpha radiation occurs?
mass goes down by 4
The positive charge is reduced by 2
What happens to the mass and charge of a nucleus during beta plus/minus decay?
Mass doesn’t change neutrons and protons have the same mass
The charge increases (beta minus) by 1 or decreases (beta plus) by 1