Radioisotopes as Tracers in Physical, Chemical, and Biological Systems - Assignment Example

Radioisotopes as Tracers in Physical, Chemical and Biological Systems Section A: Overview of Nuclear Chemistry Introduction This is a branch of Chemistry that deals with changes that occur in the nucleus of an atom (Bishop, 2012). Protons and neutrons are called Nucleons, and their total number is known as the mass number or Nucleon number. A particular nucleus, with a specific atomic number and mass number, is commonly known as a Nuclide. A nuclide is represented by the element’s symbol, the atomic number (Z) as the subscript and mass number (A) as the superscript, both written on the left-hand side of the symbol. For instance, A Uranium nuclide with 92 protons and 146 neutrons is represented as shown below; Alternative representations are Uranium– 238 or Nuclear Stability Neutron-to-proton ratio determines nuclear stability. The protons repel one another due to an Electrostatic Force between them. Neutrons are attracted to the protons and to one another by the Strong Force. Therefore, the higher the neutron-to-proton ratio, the greater the stability of the nucleus. A total of 264 nuclides is stable in nature and fall within the Band of Stability shown in figure 1.0 below. Nuclei with the number of protons above 83 are unstable. Those with 83 protons or less are either stable or unstable depending on the neutron-to-proton ratio. Unstable nuclides are referred to as Radioactive Nuclides. They undergo one or more nuclear reactions known as Figure 1.0 The Band of Stability (Faiers, 2013) Magic Numbers These are certain numbers of protons and neutrons that isotopes that have them are more stable than the rest. The magic proton numbers are 2,8,20,28,50,82,114 while magic neutrons are 2,8,20,28,50,82,126,184. Radioactive Decay Law It is a law that predicts how the number of undecayed nuclei of a certain radioactive substance decreases with time (Fendt, 2010). N = NOe-λt Where N is the number of undecayed nuclei at time t, No, the number of initially available nuclei and λ is the decay constant. Radioactive Decay Rate This rate of a radioactive decay process is described using Half-Life, which is the time required for a half of the sample to decay. Carbon-14 undergoes beta emission to form Nitrogen-14 and has a half-life of 5730 years. This means that after 5730 years, half of a sample of carbon-14 will have decayed to Nitrogen-14 and half of the sample will be remaining (PhysicsNet, 2010). T1/2 = Types of Radioactive Emissions and Nuclear Equations For unstable atoms, one way to gain stability is particle emission. Alpha particle emission An alpha particle is released in the form of a helium nucleus; two protons and two neutrons. In nuclear equations, it is written as α or. The radioactive nuclide changes into another element of lower atomic number by 2 and a lower mass number by four. Uranium-238 undergoes alpha emission as shown below. + (1) Beta Particle Emission Radioactive nuclides with a very high neutron-to-Proton ratio reach a more stable state through beta (β) emission. This involves the conversion of a neutron to an electron and a proton. The electron (e-) which is the beta particle is ejected from the atom while the proton remains in the nucleus. In nuclear equations, the beta particle is represented as, or β or β-. For instance, Iodine-131 is a beta emitter; + (2) The resulting nuclide has a same mass number and a higher atomic number by 1. Positron Emission and Electron Capture Radioactive nuclides with a slight neutron-to-Proton ratio reach a more stable state through either Positron Emission (β+) or Electron Capture.In both cases, the resulting nuclide has an atomic number lower by 1 and the same mass number. Positron emission involves changing of a proton into a neutron and Positron (e+). The neutron remains in the nucleus while the positron moves out at a very high speed. In nuclear equations, the positron is denoted as β+ or . Potassium-40 undergoes positron emission as shown below. + (3) Electron capture involves a proton capturing an electron to form a neutron. Iodine-125 undergoes electron capture as shown below. + (4) Gamma Rays Emission Radioactive decay is associated with energy release. Some of this energy is kinetic while some is given out as Gamma radiations. Cesium- 137 is an example of a beta emitter that releases gamma rays. Gamma ray emission neither changes the atomic or mass number of the nuclide. + + γ (5) Nuclear Fission and Nuclear Fusion Nuclear fusion involves two or more atomic nuclei joining to form a heavier nucleus. Nuclear fission, on the other hand, involves the nucleus of an atom splitting into two or more smaller atomic nuclei. Both processes are accompanied by the release of enormous amounts of energy. Nuclear weapons are prepared using either of the two processes. Atomic bombs result from nuclear fission, while hydrogen bombs are a product of nuclear fusion. Radioisotopes as Tracers in Physical, Chemical and Biological Systems Isotopes are the two more forms of an element whose atoms have a same proton number and different mass numbers due to a different neutron number. Unstable isotopes undergo radioactive decay and are referred to as Radioisotopes. A Radioactive tracer is that chemical compound whose one or more atoms of an element are replaced by a radioactive isotope of the same element. The process of creating a radioactive tracer is known as Radio Labeling. Working Principle of a Radioactive Tracer After radio labeling, chemical reaction mechanism can be observed through the tracing of the radioisotope’s path from reactants to products. Hence, radioactive tracers can be used in plants, animals or even human beings to follow the movement of specific chemicals. Radioactive decay is an energetic process; hence the radioisotope can still be detected even when in relatively small concentrations by use of Geiger of scintillation counters (Boundless Physics, 2014). Section B: Applications of Radioactive Tracers Biological Systems The phosphorus uptake rate in Plants: Plants that take phosphorus quickly by the roots from the soil are likely to give higher yields at low expense. Biologists can use radioactive tracers to determine which plants have a higher phosphorus uptake rate. A small amount of the radioactive phosphorus-32 is added to fertilizers, and the rate of radioactivity at the leaves measured. Pesticide Levels: the levels of pesticides in plants, run-off water and in the soil can be determined using radioactive tracers. A particular pesticide can be mixed with a known radioisotope, say chlorine-36. This can then be applied to test plants and radioactivity measurements made after a particular period. Tracers in Medicine: abnormalities in body processes can be detected using radioactive tracers. Some elements have been observed to concentrate in certain body parts. For example, Potassium concentrates in the muscles, phosphorus in ones and iodine is mainly found in the thyroid. The thyroid gland can be monitored using iodine-131. When a patient takes an iodide salt labeled with iodine-131, most of it will concentrate in the thyroid gland. Radiations emitted by the radioisotope can be captured using a special camera, and an assessment of the image can give a lot of information about the gland. Positron Emission Tomography (PET): this is a technique used to check essential body functions such as oxygen use and blood flow. Radionuclides with short half-lives such as Oxygen-15 are used. These radionuclides undergo positron emission and when the positron meets an electron, two gamma rays that move in opposite directions are emitted. These radiations are used by a scanning machine and powerful computers to determine the functioning of an organ (Science Learning, 2009). Chemical Systems Separation procedure testing in analytical chemistry: Radioactive tracers use in path following of a certain substance in a chemical separation is quick, specific and easy to use. They are also used in the separation parameters determination. In chromatographic techniques, tracers are used in the actual location of a particular fraction. The solubility product constant measurement: radiotracers are crucial in the solubility constant determination of sparingly soluble salts and also in studies of lowly concentrated substances. Isotopic Exchange Reactions’ occurrence and properties are well studied using radiotracers. Chemical Reaction Mechanisms: verification of proposed reaction mechanisms applies radiotracers. An example is various atoms equivalence testing in molecules. Complex chemical reactions steps determination: Radioactive tracers are put in molecules of reactants and their movement monitored. Carbon- 14 radioactivity was used by scientists to determine the steps involved in Photosynthesis. Physical Systems Dating: Radioactive isotopes are used in age determination of various objects. The concept of half-life is employed, and the age of even the most ancient objects can be estimated. Carbon-14 is paramount in radiocarbon dating. A small amount of it naturally produced in the upper atmosphere enters the tissues of living things though in small quantities. When the living thing dies, no more carbon-14 uptake takes place. The amount in the tissue decays and the decay process can be used to determine the time of death of the animal even after so many years. Carbon-14s suitability in dating is mainly due to its long half-life of 5370 years. Water pipe leakages: Water containing Tritium is let to flow in a water pipe suspected to be having leakages. The leaking position is identified by locating traces of tritium on the ground near the water pipes using Geiger counter. Other Physical applications of radioactive tracers include smoke detectors that use, Luggage inspection for explosives where is used among others. Radioactive Waste Management in Hospitals as an example of Radioisotopes as Tracers Radioactive tracers’ technology is now highly used in medicine. Cardiology and Oncology are some fields in which Positron Emission Tomography (PET) is an important tool especially for the diagnostic application. Of importance and concern is the disposal of the radioactive waste material emanating from these applications. According to Khan, Syed, Ahmad, Rather, Ajaz, and Jan’s (2010), radioactive waste in hospitals ought to be disposed of within the guidelines of the International Atomic Agency (IAEA). National agencies such as Atomic Energy Regulatory Board (AERB) should regulate how radioactive wastes are disposed of to ensure exposure of radiations to the environment and humans is maintained within the accepted safe limits. Reference Bishop, M. (2012, April 21). Chapter 18- Introduction to Chemistry: Nuclear Chemistry. Retrieved May 5, 2015, from Preparatory Chemistry: http://preparatorychemistry.com/Bishop_Book_18_eBook.pdf Boundless Physics. (2014, July 3). Tracers. Retrieved May 5, 2015, from Boundless: https://www.boundless.com/physics/textbooks/boundless-physics-textbook/nuclear-physics-and-radioactivity-30/applications-of-nuclear-physics-192/tracers-721-7736/ Faiers, A. (2013, November 27). Chemistry in Perspective. Retrieved May 4, 2015, from ChemBook: http://www.chembook.co.uk/chap3.htm Fendt, W. (2010, February 4). The Law of Radioactivity. Retrieved May 5, 2015, from Walter-Fendt: http://www.walter-fendt.de/ph14e/lawdecay.htm Khan, S., Syed, A., Ahmad, R., Rather, T. A., Ajaz, M., & Jan, F. (2010). Radioactive Waste Management in a Hospital. International Journal of Health Sciences, 39-46. PhysicsNet. (2010). Radioactive Decay. Retrieved May 5, 2015, from PhysicsNet.co.uk: http://physicsnet.co.uk/a-level-physics-as-a2/radioactivity/radioactive-decay/ Science Learning. (2009, October 20). Using Isotopes as Tracers. Retrieved May 5, 2015, from Science Learning- Sparking Fresh Thinking: http://sciencelearn.org.nz/Contexts/Just-Elemental/Looking-Closer/Using-isotopes-as-tracers Read More