...atoms are naturally produced in nucleogenic reactions, or in cosmogenic processes, such as cosmic ray spallation. New atoms are also naturally produced on Earth as radiogenic daughter isotopes of ongoing radioactive decay processes such as alpha decay, beta decay, spontaneous fission, cluster decay, and other rarer modes of decay. Of the 98 naturally occurring elements, those with atomic numbers 1 through 40 are all considered stable. At least one isotope of each element with atomic numbers 41 through 82 is apparently stable (except technetium, element 43 and promethium, element 61, which have no stable isotopes) but theoretically unstable (in that their fission would release energy) and thus possibly mildly radioactive.[10][11][not in citation given] The half-lives of elements 41 through 82 are so long, however, that their radioactive decay remains undetected by experiment. These "theoretical radionuclides" have half-lives at least 100 million times longer than the estimated age of the universe.[citation needed] Elements with atomic numbers 83 through 98 are unstable to the point that their radioactive decay can be detected. Some of these elements, notably bismuth (atomic number 83), thorium (atomic number 90), uranium (atomic number 92) and plutonium (atomic number 94), have one or more isotopes with half-lives long enough to survive as remnants of the explosive stellar nucleosynthesis that produced the heavy elements before the formation of our solar system. For example, at...
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...particular piece of material, artifact, or cultural remains. Some of absolute dating techniques are radiocarbon dating, dendrochronology, and potassium-argon dating. Radiocarbon dating is one of the most widely used techniques. This method is used to determine the age of organic substances such as bone, charcoal, shell, or wood by measuring the amount of the carbon isotope, carbon-14, remaining in them. The technique focuses on carbon-14, an unsteady radioactive isotope of carbon, which decays away at a steady rate. Organisms seize a certain amount of carbon-14 from the atmosphere when they are alive. By measuring the ratio of the radio isotope to non-radioactive carbon, the amount of carbon-14 decay can be calculated, thus giving an age for the material in question. Radiocarbon dating is usually used for determining ages up to about 50,000 years old, because dating older materials is much less accurate with this method. The relationship between the age estimates, also known as radiocarbon years and calendar years varies through time. Due to the distinctive variation in the richness of the radioactive isotope, carbon-14, archeologists must adjust the radiocarbon dates using sets of dates obtained from tree rings in the trunks of very long-lived tree species like the bristlecone pine to bring the radiocarbon years and calendar year to agreement. Dendrochronology is a method of dating based on the number of rings of growth found in a tree trunk. For...
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...for the duration of 10 weeks. Method of Assessment No. Method of Assessment Attendance for lectures, tutorials and experiments are compulsory for every student. Main Text: Kotz, J. C., Treichel, P. M., & Townsend, J. R. (2012). Chemistry & chemical reactivity (8th ed.). Belmont, CA: Thomson Brooks/Cole. Total 1. Coursework 50% a) Test 1 & 2 (15% each) b) Experiment (20%) 2. Final Examination 50% Grand total 100% Chapter Scopes FHSC1114 PHYSICAL CHEMISTRY CHAPTER 1 Principle of Chemistry Relative Atomic Masses of atoms & molecules Mass number & atomic number Atomic structure (neutrons, protons & electrons) Mole concept & conversion Avogadro’s concept Empirical & molecular formulae Isotopes FHSC1114 Physical Chemistry 1 Centre for Foundation Studies, UTAR Objectives To define relative atomic masses of atoms & molecules To define & determine mass no. & atomic no. To determine no. of neutrons, protons & electrons To understand mole concept & Avogadro’s concept To determine the empirical & molecular formulae Structure of An Atom Atomic Composition 3 subatomic particles made up all atoms: Electrically positive protons Electrically neutral neutrons Electrically negative electrons Table: Properties & Location of Protons, Neutrons & Electrons In Atom Subatomic Symbol Relative Mass Mass Location Particle electrical (g) (amu) charge Proton p+ +1 1.6726 1 In the x 10-24 nucleus...
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...Relative Atomic Masses and the Mole – Early Method When John Dalton proposed his atomic theory, he stated that the atoms of each element had a characteristic mass. He carried out experiments to determine the relative atomic mass of each element. To do this, he had to establish a standard because a single atom was too small to weigh. The standard he chose was that the mass of hydrogen would be set equal to 1.000. In a simple experiment, Dalton would measure the grams of an element such as sulfur that reacted with 1.00 gram of hydrogen. For sulfur, the reacting mass was found to be 32.0 grams, and so 32.0 was the relative mass of sulfur with respect to the standard hydrogen. (Note: The current standard for atomic mass is the most abundant isotope of carbon, C-12, with an assigned mass of exactly 12.000 amu.) The following activity will demonstrate how the relative mass method works. 1. Weigh five of the red color balls to three decimal places. Be sure to tare out the mass of the plastic cup. Record the mass in the table below. 2. Weigh five colorless balls. Record mass. Weigh five green balls. Record mass. 3. Set the “Relative Mass” of the red balls equal to 1.000. Calculate the relative mass of the colorless and green balls by dividing their mass by the mass of the red balls. 4. Now, weigh 1.000 gram of red balls. Try to get the mass as close as possible to 1.000 gram. Count the number of red balls in this mass and record...
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...Isotopes are “any of two or more forms of a chemical element, having the same number of protons in the nucleus, or the same atomic number, but having different numbers of neutrons in the nucleus, or different atomic weight” (Dictionary.com). There are many different isotopes in this world, some more common than others. Krypton 85 and Copper 67 are just two of many other isotopes. Krypton has a very high boiling and melting point, at 153.4° C for boiling point and 157° C for a melting point (Chemistry Learner). It was found in 1898 by a Scottish chemist and physicist Sir William Ramsay with English chemist, Morris William Travers (Chemistry Explained). They let the air evaporate slowly after cooling it enough to make it in liquid form; at...
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...Pre VCE-Physics Assessment Task 2010 NAME:________________________________________ ------------------------------------------------- PRESENTATION OF A NUCLEAR ISSUE This is an essay which is completed during a double period of class time, under test conditions, on the approved proforma. You must emphasize the physics of the topic by showing decay chains, types of radioactivity involved, and give examples of expert opinions. All work, except the research (some will be done for homework), will be done during class under test conditions. All of your resource material must be stapled to your presentation for verification purposes. Contexts 1. Development of ‘the bomb’ (Resource link - http://fas.org/nuke/index.html) For example: early discoveries in nuclear physics, leading to the Manhattan project; ethical and safety issues surrounding the development and use of atomic weapons, and the dilemma of the scientists involved; uranium, plutonium, hydrogen and neutron bombs. Or 2. Nuclear power For example: nuclear reactors - conventional and breeder; safety record of the nuclear industry; potential problems and precautions; case studies of nuclear accidents; fusion. Or 3. Radiometric Dating For Example: Principles and issues of radiocarbon dating of coal, fossils, relics and historical documents. Potassium argon dating of rock. (Eg. Turin Shroud). Or 4. Radioactivity and medicine For Example: Use of radioactively labelled amino acids...
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...to 62,000 years. Archaeology and other human sciences use radiocarbon dating to prove or disprove theories. Over the years, carbon 14 dating has also found applications in geology, hydrology, geophysics, and atmospheric science. Not all materials can be radiocarbon dated. Most, if not all, organic compounds can be dated. Samples that have been radiocarbon dated since the inception of the method include charcoal, wood, twigs, seeds, bones, shells and water, among others. When plants during photosynthesis they include a certain amount of 14C, the isotope in the atmosphere matches the same level approximately. Through photosynthesis Carbon dioxide is taken in by the plant, which is also ingested by animals, therefore every living organism is continually exchanging carbon-14 with its surrounding area as long as it lives. On the other hand when the organism dies the exchanges stops, so the amount of carbon-14 slowly decreases by radioactive beta decay with a half-life of 5,730+-40 years, half-life is the period of time it takes for the amount of a substance undergoing decay to decrease by half. There are three main types of techniques which are used to measure carbon-14 content of any given sample: gas proportional counting, liquid scintillation counting, and accelerator mass spectrometry. Firstly counting proportional counting is a conventional radiometric dating technique, which counts the quantity of beta particles that are produced by a given sample. A product of radiocarbon...
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...Radioactive Isotopes Introduction: - Radioactive isotopes are kind of isotopes, which have an unstable nuclide and react in assorted ways, they are derived from isotopes that also hold an unstable nucleus but they do not react as radioisotopes do. These factors are categorized by the extra energy which is present in them and which would be used to react and produce some other particle. The reaction, which would result in various emissions of Gama, rays, alpha particles, beta particles. The reaction, which causes these emissions, is called radioactive decay (Radioactivity). The discharge of the radioactive decay is harmful in various ways, only due to the progress in technology now these disadvantages have been converted to advantages and now radioisotopes are used in several facial expressions, which also let in various medical aspects, which would be compensated in the report. The concept of Radioactivity was found by a French physicist, Antoine Henri Becquerel. As most of the discoveries, this also was by a very honest observation and accidental. During the research of phosphorescent materials (The elements which glow in black). Studying Uranium for his research, he kept the uranium on the photographic film, it was a routine for him to hold it under the sunlight for some days and then examine it later. On a cloudy day, he kept the film and the uranium inside. Later on some days he took an observation when he watched the video, the image of the uranium appeared in the film...
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...type of metal that can be radioactive or nonradioactive, in other words it can be stable or unstable. Caesium 137 is an isotope of Caesium, it is radioactive, or unstable. It is a very familiar and common radioactive isotope, for example it is more environmentally compelling or important than another isotope of Caesium like Caesium 134. Caesium 137 along with several other radioactive isotopes were discovered in the 1930’s by Glenn T. Seaborg. Although Caesium was first discovered as non radioactive in water in Germany by two germans named Gustav Kirchhoff and Robert Bunsen (Cesium, Radiation Protection). Before going into the science behind Caesium 137 I will explain what an isotope and a radioisotope is. All elements naturally occur as isotopes, they are basically atoms with a different amount of neutrons. For example, Caesium 137 and Caesium 136 are both isotopes of the element Caesium. We can tell these isotopes apart by naming them by their total mass numbers. The total mass numbers are calculated by adding the number of protons with the amount of neutrons. Each isotope has a different mass number, Caesium 137 has 82 neutrons and 55 protons, therefore it is labelled Caesium 137, as 82 added by 55 equals 137. The mass numbers of isotopes also indicate the atomic weight of the isotopes, Caesium 137 is 137 atomic mass units or 137 u. The atomic mass of the elements are decided by the mass number of their average isotope. Regular Isotopes always maintain the same...
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...Biological Study 1. Abstract 2. Introduction In recent years, stable isotope records in speleothems (i.e., calcium carbonate deposits found in caves) have become more and more important as proxies of past climate variability (e.g., Spotl and Mangini (2002), Fleitmann et al. (2004), Harmon et al. (2004)). Speleothems, whiczare found in most continental areas provide high resolution records and can be precisely dated by U-series (Scholz and Hoffmann (2008)). The stable isotope signals of carbon δ13 C and δ18 O recorded in stalagmites are the most widely used proxy to reconstruct past climate changes. The isotopic composition of the drip water which feeds the stalagmites is influenced by several climate dependent processes occuring i) above the cave (e.g., geographical position, amount and type of vegetation, rainfall amount, temperature), ii) in the soil/karst zone (e.g., flow path of the solution, pCO2, host rock dissolution occuring under open or closed conditions iii) in the cave and on the surface of the speleothems (e.g., drip rate, pCO2). Inside the cave calcite precipitation results from the difference in pCO2, leading to a progressive degassing of CO2 from the drip water and hence, to an increase in supersaturation with respect to calcite. The isotopic composition of the precipitated calcite depends on the isotope value of the drip water and on isotope fractionation processes between the different species involved in calcite precipitation...
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...Radiometric dating is when the amount of Carbon-14 is analyzed in a specimen that was once living compared to the amount of Carbon-14 in a sample that is currently living. The important information that radiometric dating is based on is that Carbon-14 has been produced at a constant rate in the upper atmosphere for all of time. Furthermore, the half-life of Carbon-14 is 5,730 years and it will never change. When an element has an atomic number greater than 82, it is radioactive. When the nucleus of an elements does not have an even number of protons and neutrons, with the exception of hydrogen and 5 others, the element is radioactive. Also, when the nucleus has either too many or too few nucleons in one or more shells, the element is radioactive....
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...acromegaly. It is the isotope used in radiocarbon dating and radiolabeling. Radiocarbon dating is determining the age of different organic materials, by measuring the amount of carbon-14 in a material, compared to the amount of carbon-12. Carbon dating makes use of the fact that some atoms – radioactive atoms – change over time into other types of atoms in a natural process known as radioactive decay. 2) Americum-241, is used as a component in household and industrial smoke detectors, where a small amount is used in an ionization chamber inside the detector. Americium-241 is the only isotope of americium to have widespread commercial use. It is the radiation source for a number of applications: • medical diagnostic devices • research • fluid-density gauges • thickness gauges • aircraft fuel gauges distance-sensing devices, all of which utilize its gamma radiation. A mixture of americium-241 and beryllium provides a neutron source for industrial devices that monitor product quality. Two examples are devices for nondestructive testing of machinery and gauges for measuring the thickness of glass and other products. 3) Iodine-131, is used in nuclear medicine both diagnostically and therapeutically. Examples of its use in radiation therapy include the treatment of thyrotoxicosis and thyroid cancer. Diagnostic tests exploit the mechanism of absorption of iodine by the normal cells of the thyroid gland. As an example iodine-131 is one of the radioactive isotopes of iodine that can be...
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...ITtestPapers.com – Placement Papers, Interview Questions and Tutorials ------------------------------------------------------------------------------------------------------------------------------- 3i-Infotech Technical Paper – 9 1. A 2MB PCM(pulse code modulation) has a) 32 channels b) 30 voice channels & 1 signalling channel. c) 31 voice channels & 1 signalling channel. d) 32 channels out of which 30 voice channels, 1 signalling channel, & 1 Synchronizatio channel. Ans: (c) 2. Time taken for 1 satellite hop in voice communication is a) 1/2 second b) 1 seconds c) 4 seconds d) 2 seconds Ans: (a) 3. A dishonest shopkeeper professes to sell pulses at the cost price, but he uses a false weight of 950gm. for a kg. His gain is ...%. 4. Max number of satellite hops allowed in voice communication is : a) only one b) more than one c) two hops d) four hops Ans: (c) 5. Conditional results after execution of an instruction in a micro processor is stored ina) register b) accumulator c) flag register d) flag register part of PSW(Program Status Word) Ans: (d) 6. Frequency at which VOICE is sampled is a) 4 Khz b) 8 Khz c) 16 Khz d) 64 Khz Ans: (a) 7. Line of Sight is a) Straight Line b) Parabolic c) Tx & Rx should be visible to each other d) none Ans: (c) 8. Purpose of PC(Program Counter) in a MicroProcessor is a) To store address of TOS(Top Of Stack) b) To store address of next instruction to be executed. c) count the number of instructions. d) to store base address of the stack. Ans:...
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...constantly changing. The root of a scientist’s belief must come from a more stable foundation. Although, Old-earth and young-earth scientists agree on carbon-14 half-life, the scientists differ in areas such as finding C-14 in rocks and diamonds. To begin, we must first describe the process of radiocarbon dating. The half-life of Carbon-14 has been measured at 5,730 years. Therefore, the assumption has been made that radiocarbon dating is only valid to be used on objects older than 100,000 years. Morris (2011,63) describes the process in this way, “Carbon-14 is formed when nitrogen -14 interacts with a cosmic ray-produced neutron in the upper atmosphere”. This new isotope is only a small part of the total carbon. Within the isotope there is a ratio of Carbon-12, a stable carbon, to Carbon-14, a non-stable carbon. The isotope is incorporated into carbon dioxide, which is then breathed in by all living organisms. When living organisms are alive, the radiocarbon that is dying of is constantly being replaced. However, when the organism dies, the Carbon-14 decreases and begins changing back into Nitrogen-14 (Lutgens, 2014, 286). From here the ratio of C-12 to C-14 can be measured as the C-14 is decreasing. Christopher Weber (1982) suggests, “If we measure the rate of beta decay in an organic sample, we can calculate how old the sample is. C-14 decays...
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...The founder of the element Uranium was discovered by Martin Heinrich Klaproth. He was born on December 1, 1743, in Brandenburg, Germany. He was the leading chemist of his time and he was a pharmacist for a great deal of his life. In 1787 he become a lecturer to the Royal Artillery, and when a university was founded he was selected to be a professor in 1810 to teach chemistry. Other than Uranium Klaproth discovered the elements Titanium and the element Zirconium. Uranium's atomic number is 92 and it is highly radioactive. It can be used to make nuclear weapons, which has the power that can destroy countries. It discovered during a mineral pitchblende ( mix of uranium oxides). There is more than one type of uranium, such as there is Uranium dioxide,...
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