Isotopes

Distinguish Between Stable and Radioactive Isotopes and Describe the Conditions under Which a Nucleus Is Unstable Isotopes refer to an element that has different numbers of neutrons, but the same number of protons and electrons. Isotopes of the same element differ in the mass number but not the atomic number Mass number – number of nucleons (protons and neutrons) Carbon-13 is an isotope, as it has 6 protons and 7 neutrons. A stable isotope does not go through radioactive decay. This is because the neutrons and protons are in such a low energy level that they are unable to release energy. For each isotope there is a favoured balance of neutrons and protons so that they are held together well. If an atom has too many neutrons its starts to decay. The kinds of radiation emitted are alpha, beta and gamma particles. Radioactive decay refers to unstable isotopes constantly emitting energy (or radiation). -A stable isotope does not release radiation, but a radioactive isotope does. - A radioactive isotope releases radiation. Radiation comes in 3 forms: Alpha Beta gamma |Name |Symbols |Identity |Relative Mass |Relative Charge |Penetrating power | | | | |Hydrogen = 1 | | | |Alpha |a |Helium Nucleus |4 |+2 |Low (thin sheet| | | | | | |of paper) | |beta |b |Electron |1/1836 |-1 |Medium (0.5 mm of | | | | | | |lead) | |gamma |y |Electromagnetic |0 |0 |High (5cm of | | | |radiation | | |lead) | Isotopes are unstable when: The atomic number is greater than 83 or when the ratio of neutron to protons lies outside the zone of stability. (Top half…unstable region due to too many neutrons) (Bottom half due to too many protons) Describe how Transuranic Elements are Produced -Transuranic elements are those with an atomic number greater than that of uranium (92). They are artificial, and are created by bombarding large nuclei with positive particles of a carbon and helium, which are done in particle accelerators -There have been 23 transuranic elements made. (Ununoctium lies at 118) Describe How Commercial Radioisotopes are produced -Commercial radioisotopes are produced in a similar way to transuranic elements, as elements are bombarded with neutrons to create a radioisotope. This usually takes place in a nuclear reactor. Identify instruments and processes that can be used to detect radiation -Photographic Film: A badge covered in photographic film, which gets darker the more it’s exposed to radiation. Workers usually wear these badges so that they know how much radiation they have been exposed to. -Cloud Chamber: Contains an amount of supersaturated alcohol or water vapour. When radiation passes through this, it ionizes the air which causes droplets of alcohol to appear. This shows the path of the radiation. -Scintillation counter: When a substance is irradiated with alpha, beta or gamma rays, it gives of a flash of light. This flash of light is put through a photomultiplier, making this process visible to observers. -Geiger Muller counter: Argon atoms that are in a Geiger tube become ionised when in contact with radiation. This creates an electrical pulse that is detected by the Geiger counter. Identify one use of a named radioisotope Describe the way in which the above named industrial and medical radioisotopes are used and explain their use in terms of their properties - Co60 is a radioisotope used for industrial purposes. It is used to detect faults in industrial material, as it emits gamma rays (very strong penetration). Beams of radiation are directed at the object in question from a closed source of CO60, and the radiation shows up on radiographic film on the other side of the material. It is clear if there are cracks or holes in the material if more radiation shows up on the radiographic material. - It can also be used for food irradiation (ionizing radiation removes harmful bacteria.) - Benefits: It can be reused, and its not very problematic once disposed (due to its short half-life from a waste disposal perspective, which is six days). Very ideal for getting rid of unwanted substances (eg microscopic bugs in food) - Problems: Extremely dangerous if a person encounters it exposed. It can create unknown and unexpected chemicals in food when applied. It destroys thiamine (vitamin B). - Technetium 99 is a medical radioisotope, which emits beta rays. It is used to detect developing brain tumours and blood clots in the human body amongst other things. It is injected into the blood along with tin compounds, which it then binds with red blood cells. - Benefits: It has a short half life (roughly six hours). A gamma camera can easily detect the low energy gamma rays that pass out of the body. - Somewhat expensive to produce compared to other radioisotopes. It can potentially kill healthy cells in the body. Process Information from Secondary Sources to describe the recent discovery of a particular element -Rutherfordium (104) was identified in 1966 at the “Joint Institute of Nuclear Research” at Dubna (Soviet Russia) -242Pu (plutonium) was bombarded with accelerated 22Ne ions (Neon). Gradient thermo chromatography was then used to separate the reaction products (reaction products were converted into chlorides due to a reaction with ZrCL4 -The reaction is: 242/94pu + 22/10Ne ( 264/104Rf (264/104RfCL4 - In 1969 Californium-249 was bombarded with carbon-12 atoms in order to chemically separate Rutherfordium so that it is isolated and alone. -The equation used to achieve this is: 249/98Cf + 12/6C (257/104Rf + 4n. Bibliography http://www.webelements.com/periodicity/description/ -The source is pretty valid, as the author and source of the information is in plain view. However for this type of assignment it isn’t very useful, as the information it provides on Transuranic elements is extremely brief. HSC Chemistry Excel by Jim Stamell 2008 -Extremely valid, as the book openly reveals all information regarding its creation and history. Very useful also, as there is lots of detailed and relevant information regarding this assessment. http://www.hsc.csu.edu.au/chemistry/core/identification/chem925/925net.html -Very valid, as its website address makes perfectly clear. It leaves lots of contact details and information regarding its validity. It is somewhat useful, and having the exact questions is a plus, however its very brief, and should be used for cross-referencing. http://environmentalchemistry.com/yogi/periodic/Rf.html Relatively valid, as it has an information page and information about the creation of the site is available for all to see. It provides useful information and Transuranic elements, however that’s about it. http://backreaction.blogspot.com/2008/11/technetium-99.html The validity is somewhat compromised by the fact that there is no information regarding the creation of the page. Furthermore it is a blog website, where random people post there knowledge up on to the website. When taking this into account this really isn’t any more valid than Wikipedia. It provides useful information on radioisotopes and their properties; however it’s a good idea to cross reference. http://www.hps.org/publicinformation/ate/faqs/radiationdetection.html Very valid, information about the creation of the site is available to everyone, however the website was last updated in December 2008. New developments could have occurred and this website is incapable of showing this. The information it gives is very useful about devices that can detect radiation, and it explains it well.