1.What charge does a neutron have? 1
2.What is the mass of an electron? 1/2000
3.What is another name for proton number? Atomic number
4. What does relative atomic mass mean? The relative atomic mass is a measure of the mass of one atom of the element.
(Chemistry) The ratio of the average mass per atom of the naturally occurring form of an element to one-twelfth the mass of an atom of carbon-12.
How small is an atom from TED Ed youtube.com

5.2 Radioactivity

5.2.1 Detection of radioactivity
• Demonstrate understanding of background radiation
Half of background radiation on Earth is naturally radioactive gases in the atmosphere. Some of it comes from natural sources and some comes from artificial sources. Radon is produced in decay(break up) of Uranium ore.
Background radiation from BBC GCSE Bitesize
Background radiation comes from:
•Cosmic rays from space
•Radioactive rocks in the ground
•Nuclear tests / accidents / bombs

• Describe the detection of α-particles, β-particles and γ-rays (β+ are not included: β-particles will be taken to refer to β–)
For the detection of alphas, betas and gammas, a Geiger-Müller counter is used from www.darvill.clara.net
Penetrating properties of radiation from BBC GCSE Bitesize
Penetrating properties of radiation from unitednuclear.com

5.2.2 Characteristics of the three kinds of emission
Radioactive emissions occur randomly over space and time. Radioactivity(A radioactive emission) is a process in which atoms with unstable nuclei spontaneously decay(break up). We cannot tell which atoms will go decay the next.

Radioactive decay(disintegration): The spontaneous breakdown of a radioactive nucleus into a lighter nucleus. Radioactive decay causes the release of radiation in the form of alpha particles, beta particles, or gamma rays. The end result of radioactive decay is the creation of a stable atomic nucleus.

A diffusion type cloud chamber shows a particle tracks and its ionising effects. A spark counter.

• Discuss the random nature of radioactive emission
• Identify α, β and γ-emissions by recalling
– their nature
– their relative ionising effects
– their relative penetrating abilities (β+ are not included: β-particles will be taken to refer to β–)

Radiractive decay.jpg
Table of the Properties of the three types of radioactive emission and symbols from docbrown.info
Types of radiation from BBC GCSE Bitesize
penetration of radiation.PNG
The penetrating power of α, β and γ radiation from hyperphysics

• Interpret their relative ionising effects
All of alpha, beta, gamma radiations are energetic enough to pull electrons away from atoms. The atoms that have lost electrons are charged particles of ions, and hence the name ionising radiation.
Effect of ionising on tissues from s-cool.co.uk

Ionizing radiation can break chemical bonds and easily make chemical reactions in living cells.
Ionisation ability from BBC GCSE Bitesize

Alpha and beta decay from phet
Alpha Decay
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Beta Decay
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• Give and explain examples of practical applications of α, β and γ-emissions
Uses of alpha beta gamma radiation from www.passmyexams.co.uk

applications of α
applications of α, β and γ
applications of γ

• Describe their deflection in electric fields and magnetic fields
Diagrams of deflection in magnetic fields and electric fields from hyperphysics
Deflection in magnetic andd electric field.PNG
The effects of a magnetic field on radiations.jpg

Deflecting radiation from BBC GCSE Bitesize

5.2.3 Radioactive decay
• State the meaning of radioactive decay
State that during using a- or b-decay the nucleus changes to that of a different element
Radioactivity: The emission of radiation by unstable atomic nuclei undergoing radioactive decay.
It is a process in which atoms with unstable nuclei spontaneously decay emitting subatomic particles and energy as they reconfigure into more stable forms.

Decay: 1. a spontaneous transformation of an elementary particle into two or more different particles 2. of an excited atom or molecule, losing energy by the spontaneous emission of photons

Radioactive decay: The spontaneous transformation of an unstable atomic nucleus into a lighter one, in which radiation is released in the form of alpha particles, beta particles, gamma rays, and other particles. The rate of decay of radioactive substances such as carbon 14 or uranium is measured in terms of their half-life.
• Use equations involving nuclide notation to represent changes in the composition of the nucleus when particles are emitted
nuclear decay.PNG
Nuclear equations from BBC GCSE Bitesize
Uranium 238 decay chain from www.unitednuclear.com

5.2.4 Half-life
• Use the term half-life in simple calculations, which might involve information in tables or decay curves
• Calculate half-life from data or decay curves from which background radiation has not been subtracted
The HALF-LIFE of an atom is the time taken for HALF of the radioisotopes in a sample to decay. The decay of radioisotopes can be used to measure the material’s age.

The half-life of radioisotopes varies from seconds to billions of years. from ndt-ed.org
Half life.jpg

Science in Focus Radioactivity S100LS05 Lammas Science Published on 15 Nov 2012
Half life from BBC GCSE Bitesize
Half lives of various elements from no-nukes.org

Experiment (Radioactivity / Half life )

Aim: To simulate decay by rolling die and to estimate the decay constant and half-life from the decay curve. Apparatus: 100 six sided die.

  1. Count and record the total number of die. Each dice must have the same number of sides (for our experiment we will use six-sided dice.)
  2. Roll all the die at the same time onto a level table. A plastic container can be used to hold all the dice so they can be easily rolled simultaneously. The table should have some friction so that the dice don't slide off the edge. If some of the dice stack up, gently nudge the table so they all lay down flat on the surface.
  3. Remove all the dice which turn up "1".
  4. Count and record the number removed.
  5. Repeat the experiment with the remaining die.
  6. Record the time interval between each roll as one second and continue the experiment until no dice
    remain from the original batch.
  7. Plot the decay curves using total number of dice (as a function of time) as well as the activity of the
    sample (as a function of time).
  8. Estimate the decay constant and half-life from the sample.
  9. Repeat steps 2-8 except remove all the dice which turn up "1" or "2".
  10. Interpret the value of the decay constant you find from the graphs, is it what you could have expected?
  11. Include your graphs and data tables along with your report.

  • Giancoli, 6th Edition Physics

Assessment Criteria:
  • Time: 1.0 hrs.

Due Dates: 13th December 2013

5.2.5 Safety precautions
Recall the effects of ionising radiations on living things from BBC GCSE Bitesize
• Describe how radioactive materials are handled, used and stored in a safe way

Radioactive Waste Management from world-nuclear.org
After a fuel can has been in a reactor for three or four years, it must be removed and replaced. The amount of uranium-235 in it has fallen and radioactive products are building up. Some are very dangerous:
  • Strontium-90 and iodine-131 are easily absorbed by the body. Strontium becomes concentrated in the bones; iodine in the thyroid gland.
  • Plutonium-239 can be used as a nuclear fuel and in nuclear weapons. It is highly toxic. Breathed in as dust, the smallest amount can kill.
Waste from a nuclear reactor is taken to a reprocessing plant. Remaining waste will be stored with thick shielding around it. Some of the isotopes have long half-lives, so safe storage will be needed for thousands of years.

Fill in the blanks below.
Nuclear energy is a non-renewable energy resource. In nuclear power station, the chain reaction inside the reactor creates heat, which heats and turns water into steam to rotate turbines, which drive generators to produce electricity. The nuclear fuel is safe to handle before they go to reactor. It needs to be handled by robot arms and heavy shielding for safety when they come out from the reactor. Nuclear power stations do not create atmospheric pollution but the small amount of waste produced is very dangerous. It must be sealed up and buried for many years to allow the radioactivity to die away. Nuclear power is reliable but a lot of money should spend on safety.

Go visit radioactivity from www.darvill.clara.net

5.1 The nuclear atom

5.1.1 Atomic model
• Describe the structure of an atom in terms of a positive nucleus andnegative electrons
Atomic structure.jpg
Image of atomic structure from http://www.docbrown
• Describe how the scattering of α-particles by thin metal foils provides evidence for the nuclear atom
Schematic diagram of apparatus used by Geiger and Marsden.jpg
Schematic diagram of apparatus used by Geiger and Marsden
Images from chemeddl.org
Rutherford alpha particle deflection.jpg
Conclusion from Rutherford scattering experiment:
Atom must have a dense positively charged region containing most of the atomic mass.
Development of atom model from Cambridgephysics
Rutherford scattering experiment applet from Florida state university

Rutherford Scattering Questions from Hyperphysics

1. Why was the observation of large angle scattering of alpha particles surprising?
2. Under what conditions can you get scattering at angles greater than 90 degrees?
3. Besides the mass of the target, what else determines the scattering angle?
4. How can you determine the distance of closest approach to the target?
5. What was the evidence of a new type of force from the observation of the scattering?
Rutherford Scattering
Click to Run

Rutherford experiment from cyberphysics.co.uk

5.1.2 Nucleus
• Describe the composition of the nucleus in terms of protons and neutrons
• State the charges of protons and neutrons
• Use the term proton number Z
• Use the term nucleon number A
• Use the term nuclide and use the nuclide notation ZAX

proton: A positively charged elementary particle, found in atomic nuclei in numbers equal to the atomic number of the element.
neutron: Neutral, same mass as proton
electron: A negatively charged elementary particle in an atom.
nucleon: A proton or a neutron, especially as part of an atomic nucleus
nuclide: An atomic nucleus identified by its atomic element and its mass number. For example, a carbon-14 nuclide is the nucleus of a carbon atom, which has six protons, with mass number 14 (thus having eight neutrons).
ex) Nucleus is a generic term of nuclide. If nucleus is a country then nuclide is like China. There are about 3000 nuclides.

• Use and explain the term isotope
• Balance equations involving nuclide notation
An isotope is an atom with a different number of neutrons. e.g. O16, O17, O18
Radioisotope: An isotope that is radioactive.

BBC Higher Bitesize
Radiation and cancer from www.cancer.org

• State the meaning of nuclear fission and nuclear fusion

Nuclear fission

Highly unstable nucleus splits into two lighter nuclei, it releases energy while shooting out two or three neutrons. The splitting of the nucleus is called fission. {Natural uranium is a dense radioactive metal. It is mostly made up of two isotopes: uranium-238(over 99%) and uranium-235(less than 1%).}
nuclear fission from cyberphysics.co.uk
Nuclear fission.PNG
Image from www.nuclear-power.net
nuclear fission equations.PNG
Facts about fission products from Hyperphysics

Nuclear Fusion
Two atomic nuclei joining to make a large nucleus. Energy is released during the process of Nuclear fusion so it can also be used as a source of energy.

Where Does The Sun Get Its Energy? Veritasium Published on 6 May 2012
nuclear fusion.PNG
Image from nuclear-energy.net
Have you spotted the Earth in the solar system? Can you describe nuclear fusion? How does fusion power the Sun?
How close are we to nuclear fusion from forbes.com
What is nuclear fusion from www.iter.org

Nuclear fission and fusion from BBC Bitesize

Nuclear fusion getting closer
from science.howstuffworks.com
Interesting subatomic particle
Neutrino from Britannica

The atom song by Mr. Parr Youtube

Atomic physics revision from schoolphysics.co.uk