HISTORY OF THE PERIODIC TABLE How did the periodic table develop? Since a very long time‚ elements such as gold‚ silver‚ tin‚ copper‚ lead and mercury have been known. But the concept of elements have largely be changed since then. Many scientists did research and new scientific discoveries were found. The progress of science never ends. Lavoisier In 1789‚ French chemist Antoine Laurent Lavoisier discovered that an element is a fundamental substance that could not be broken down by
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PERIODIC CLASSIFICATION OF ELEMENTS Introduction There are 115 elements that are known at present. Some elements have similar properties whereas some others have completely contrasting properties Scientists began to look for some pattern in the properties of these elements Dobereiner’s triads In 1817‚ Johann Wolfgang Dobereiner‚ a German chemist‚ classified elements into groups based on their properties. He kept all elements having similar properties in one group. Most of his groups had three
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come across a laboratory‚ classroom‚ chemistry textbook or lecture theatre that doesn’t contain a periodic table of the elements. It required the immense research and determination of the scientist Dmitri Mendeleev to show us that all elements followed a natural form and provided us with the first decent periodic table. There are 111 elements recognised today by IUPAC and they are arranged in the periodic table in horizontal groups and vertical periods. The eight groups consist of the alkali metals
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DEVELOPMENT OF THE PERIODIC TABLE Although Dmitri Mendeleev is often considered the "father" of the periodic table‚ the work of many scientists contributed to its present form. Elements such as gold‚ silver‚ tin‚ copper‚ lead and mercury have been known since earliest times. In 1649 the first scientific discovery of an element occurred. Hennig Brand‚ a German chemist‚ treated urine to a series of processes that resulted in the production of the element phosphorus. Over the next 200 years
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the properties of the elements recur in the same pattern. With the works of these scientists‚ the periodic table was created as well as the periodic law. With this set‚ scientists as of today had been able to organize the elements without much trouble and were able to discover unknown elements. Although there are many elements in the world and many of them have not always been known of‚ the periodic table had been created to classify these elements as well as the table’s corresponding patterns and
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REVIEW OF LITERATURE A discussion regarding use of psychometric test has been carried out in May 2001‚ published by centre for the economics of education by Andrew Jenkins From the article: This paper surveys the literature on the use of psychometric testing by employers‚ and considers whether information on psychometric testing can be used to make deductions about changes in the demand for skills in the economy. The standard approach to measuring the demand for skills‚ and
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Appreciation Forgotten The fairy tale of The Nightingale and the Rose‚ by Oscar Wilde published in 1990‚ is a story of the consequences of not appreciating creation. It is also a story of men not appreciating the sacrifices that women make. This passage‚ from The Nightingale and the Rose‚ foreshadows the consequences of not a appreciating nature. It then symbolizes pregnancy and childbirth‚ a sacrifice many women make that men take for granted. The first part of the passage uses
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financial ratio. Financial ratios may be calculated in different ways‚ using different figures (Gibson and Cassar‚ 2005). Financial Ratio helps to outline a large volume of financial data into a concise form so it is easy to interpret and conclude the performance and position of the firm. 1.2 Ratio Analysis There are two steps that ratio analysis needs to be follow. First‚ the calculation of ratio has to be done. Second‚ the ratio has to compare with predetermined standards. Predetermined standards can
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The Periodic Table Notes History of the Periodic Table * Two main contributors * Dmitri Mendeleev * Henry Moseley Dmitri Mendeleev – Russian * 1869: published his periodic table with the 63 known elements * Arranged the first periodic table in order of increasing atomic masses Henry Moseley – British * 1913 revised Mendeleev’s periodic table * Today’s periodic table * Arranged in order of increasing atomic numbers What is the difference between Mendeleev’s
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Introduction: The periodic is a table of the elements‚ organized in order of increasing atomic number. Elements that have similar chemical properties and electronic structures appear in vertical columns‚ or also called groups. The Periodic Law states that when elements are placed in order of increasing atomic number‚ their physical and chemical properties display a periodic pattern. The purpose of the lab was to discover how two periodic properties‚ atomic radius‚ and first ionization energy‚ vary
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