Radioactivity & Particles (7.1-7.26) Flashcards
What are atoms made of?
Protons, neutrons and electrons
Atomic number is…
the number of protons in the nucleus of an atom
Mass number is…
the total number of protons and neutrons in the nucleus of an atom
What is an isotope?
An atom of the same element that have same number of protons (atomic number) and different number of neutrons (different mass number).
Three types of ionising radiation
Alpha (α), Beta (β) and Gamma (γ)
What is ionisation?
Ionisation is when an atom loses or gains an electron, causing it to become an ion (an atom which is positively or negatively charged)
Alpha (α)
- Strong ionisng
- few centimetres in air
- stopped by paper
- nature of radiation is helium nucleus
Beta (β)
- Moderate ionisng
- 1m in air
- stopped by aluminium (5mm)
- nature of radiation is fast moving electron
Gamma (γ)
- Very weak ionisng,
- 1km in air
- stopped by lead (10cm)
- nature of radiation is electromagnetic wave
Effects of Alpha decay
- 2 protons and 2 neutrons are lost
- Mass number decreases by 4
- Atomic number decreases by 2
Effects of Beta decay
- 1 neutron is converted to an electron (lost from the atom) and proton
- Mass number is unchanged
- Atomic number increases by 1
Effects of Gamma decay
- Energy is lost from an atom in the form of an electromagnetic wave
- Mass number is unchanged
- Atomic number is unchanged
What can detect ionising radiation?
Ionising radiation can be detected by photographic film or a Geiger-Müller
- Counter connected to geiger-müller
- Radiation will cause photographic film to darken
Background radiation from earth and space
- Radon in air
- Graint in rocks
- Cosmic rays
- Medical equipment
- Food and drink
Does a radioactive source decreases over a periodof time?
The activity of a radioactive source decreases over a period of time and is measured in becquerels
Half life definition
Is the average time taken for half the original number of nuclei in a sample of a radioactive element to decay
Uses of radioactivity in industry and medicine
- Gamma radiography
- Medical tracer
- Gauging
- Radiotherapy
- Pipe tracers
- Sterilisation
- Carbon dating
(DESCRIBE ALL OF THESE 7.14)
Contamination
Occurs when material contains radioactive atoms is deposited on materials, skin, clothing, or any place where it is not desired.
Irradiation
The process by which and object is exposed to radiation
Gamma radiography
- Gamma
- Gamma ray cameras are
- Used to look inside objects
Airport security
Medical tracers
- Radioactive tracer put in body (swallowed / injected)
- Detector put around you
- Computer generates an image
Gauging
- Coal absorbs a lot of radiation
- If only a small amount of radiation is detected back after it is reflected by what you are trying to gauge, lots of coal is present
Radiotherapy
- High doses of radiation are directed at cancer cells
- Cancer cells are killed
Pipe tracers
- A radioactive material which emits gamma radiation with a short half-life is put in the water
- A detector is placed above the pipe
- A spike in deteted radioactivity suggests a leak in the pipe
sterilising
- Medical equipment irradiated
- Kills all living matter on tools (e.g. bacteria)
Carbon dating
Radiocarbon dating measures the level of an isotope called Carbon -14.
Measurement of the beta decay activity of a buried piece of wood provides a measurement of the time elpased since it was living and in equilibrium with the atmosphere
Dangers of ionising radiation
- That radiation can cause mutations in living organisms
- That radiation can damage cells and tissue
- The problems arising from the disposal of radioactive waste and how the
associated risks can be reduced
Radioactivity unit
Becquerels (Bq)
The amount of radiation given out by a substance
One Becquerel = One particle emitted per second
Nuclear Fission
The process where heavy atoms are split into smaller, lighter atoms. This releases energy.
Nuclear Fusion
The process where lighter atoms are forced to join together to make heavier atoms. This releases energy.
Radioactive Decay
Within the core of the Earth, radioactive isotopes of elements such as uranium, thorium and potassium provide a large proportion of the heat within the Earth through radioactive decay.
Fission of U-235
A slow moving neutron is absorbed by a uranium 235 nucleus.
The resulting uranium 236 nucleus is unstable.
It splits to form two smaller daughter nuclei, three neutrons and gamma radiation.
Chain Reaction
The three neutrons produced by the fission may hit other nuclei of uranium 235, causing the process to repeat.
For a chain reaction to occur, there is a minimum mass of uranium 235 required. This is known as the critical mass.
Control rods
Absorb neutrons to prevent a chain reaction from happening too quickly
Made from boron
Moderator
Slows down neutrons by absorbing KE energy
Made from graphite or water
Role of shielding around a nunclear reactor
Prevent any radiation escaping, even neutrons
Made with concrete layer
Nuclear fussion results in…
a loss of mass from smaller nuclei
Nuclear fussion is the…
energy source for stars and sun
Why does nuclear fusion dont happens at low temperatures and pressures?
For nuclear fusion to occur, very high temperatures are required to overcome the repulsive force between the positively charged nuclei of each isotope.
High pressures are also needed to increase the chance of fusion between the nuclei.
