History of Periodic Table - Term Paper Example

HISTORY OF PERIODIC TABLE Introduction Periodic table refers to a table that illustrates periodic system that has chemical elementsarranged in order of atomic numbers. However the prerequisite to the establishment of the periodic table was the initial discovery of the individual different elements (Scerri, 2006). Chemistry has always made attempts to arrange these elements in a manner that reflects similarities in their properties. The periodic table that is currently in use lists the elements according to their atomic numbers (Scerri, 2011). The atomic number refers to the total number of protons present in an atom’s nucleus. However, historically, scientists tried to organize the elements using their relative atomic masses (Scerri, 2011). This was because the idea of using an element as being made of protons, electrons and neutrons was not yet developed. Nonetheless, the basis that is used on the modern periodic table has been used to predict properties of undiscovered elements even before the idea of atomic numbers came to be. This essay therefore shall give a chronological account of events on how the periodic table was developed to the modern one that is in existent. Additionally, charts will be used to illustrate the stages of development in the history of periodic table. Origin of the periodic table Awareness of some of the elements in the periodic table existed long before written history. They include Gold, copper mercury among others. However, it was until 1649 that the first elements came to be discovered in a scientific manner. This was Phosphorus (P) discovered by Henning Brand. By1869 up to about 18 elements had been discovered. Grouping of elements with the order of their properties began between 1817 and 1829. Johann Dobereiner had begun the grouping of elements in to triads focusing on their similarity in terms of properties. This process begun with the element strontium (Sr) which he noticed weighed somewhere halfway between the weight of barium and calcium. He further discovered a halogen triad which was made up of iodine, chlorine and bromine as well as an alkali metal triad made up of potassium, lithium and sodium. As such he postulated that there exists triad of elements in nature that the middle one has properties that are an average of the other two. Later on other scientists came to discover other elements which they further would group in to more than sets of three (Royal Society of Chemistry, n.d). It should also be noted that various attempts had been made to come up with the periodic that we use today. The few elements that were known during the earliest times were investigated by the scientist to find a pattern of arranging them. For instance, 1789 offered the earliest opportunity for trying to classify these elements. Scientists like Antoine Lavoisier made attempts to classify the elements based on the similarity in properties. As such he had the gasses, non-metals, earth and the metals. This was several decades before Johann Dobereiner would start investigating his pattern of grouping elements. Further, the list of more accurate atomic masses was made available in 1860 at Karlsruhe, Germany. This was a milestone since it provided a platform for suitable arrangement of elements. As such it aided the progress towards discovery of the modern periodic table. It therefore took the work of several great scientists; one error after the other till the current periodic table came to be. Precursor to the periodic table In 1862 the atomic weights of elements was then used to arrange different elements. This was made a reality by Beguyer de Chancourtois who ensured similar elements occurred at intervals that are regular. He positioned the elements on a cylinder to transcribe a list in order of increase in their atomic weight. Therefore, closely he vertically lined up closely related elements on a constructed cylinder with 16 mass units written on it per turn. Chancourtois was the first scientist to make the discovery of reoccurrence of elemental properties every seven elements. His table however included a few ions and compounds (Western Oregon University, n.d). An English chemist by the name John Newlands was then to propose the law of octaves. As such he stated that the elements repeat their chemical properties after every eight elements. This musical analogy faced a lot of ridicules but was then to be found insightful after publication of Meyer and Mendeleev’s works (Brewton-Parker College, n.d). Fig. 1 Musical octave that Newlands associated with elements In 1969 Dmitry Mendeleyev, a Russian chemist, did a publication of the first periodic table. This he did by writing the Mass and chemical property of each element on a card. He then arranged the labeled cards in order of increase in the atomic mass and came to a revelation that elements that bore similar qualities would appear at intervals that are regular (Freudenrich, n.d). He even went ahead to take some liberty with his periodic table and interfered with his order that had increase in masses of certain elements to enable them fit in certain groups. With this he placed tellurium which has a mass of 128 before iodine so that he can have iodine, chlorine, bromine and fluorine fall in a similar group as they had properties similar to those of iodine. Additionally, Mendeleyev also noted that reversing the elements while preserving the periodic pattern, will result in to wrong values of the atomic mass. He also left certain gaps in his table to fit the elements that he reasoned that should be in existence but are yet to be discovered. Dmitry Mendeleyev came up with a table that would predict three elements of masses 70, 68 and 45.his prediction was to be proven right by the discovery of the elements which are Germanium, gallium and scandium in the respective order. However, Mendeleyev’s periodic table bore different atomic weight as those that are listed in today’s modern periodic table. This is because, during the twentieth century, due to advancement in technology, the method for measuring the atomic weight was improved to increase accuracy thus resulting to a slight difference with that of Mendeleyev (Freudenrich, n.d). Mendeleyev succeeded in coming up with this periodic table because of his simple rule. That was elements that are similar in properties are to be placed in one group. Therefore, this implied that in the periodic table, elements that have similarities will be fitted in one column. The periodic table below explains the phenomenon of similar elements belonging to a specific group (Scerri, 2006). The yellow mark that contains hydrogen (H) at the top gives a group of elements with similar properties in a single column. This is the basic rule that Mendeleyev used to get to arrive at his periodic table putting elements with matching properties in a similar column. Fig. 2 periodic table The periodic properties of elements were critical to the discovery of the periodic table. Mendeleyev succeeded because his idea arranged the elements in a manner that as one moves across from the atoms that are lighter to those that are heavier, the properties of the elements keep periodically remaining the same. This is the reason why the name periodic table came about. The table was also came up with in manner that atoms would get bigger down the column while smaller as you move right across the period (Scerri, 2006). Fig. 3 illustrating the periodic change across different elements in the periodic table The Modern periodic table has a difference with what Mendeleyev came up with. This is due to the adjustment that can be seen on the elements added below the first set of elements in the columns. Glen Seaborg, a scientist made a discovery of transuranium elements. These are those elements with atomic numbers 94 – 102 (Scerri, 2006). The lanthanide and actinide series of elements should technically be placed below the alkaline and transition metals. However, the completion of the series of actinide elements allowed Seaborg to modify the periodic table coming up with a new design. The periodic table would have become too wide ha this elements been arranged as they should have been. Due to this, Seaborg redesigned the table and placed the elements below the other group of elements. The end result was the table shown below. Fig. 4, Modern periodic table Conclusion The efforts made by these great scientists played a pivotal role towards the establishment of the periodic table. The law of octaves even though ridiculed in the onset provided a critical analogy that would reveal a pattern of recurrent property in the eighth element along the order. Dmitri Mendeleev a Russian scientist was reorganization of elements to discover a pattern; Lord Reighlei’s discovery of Noble gasses; William Ramsey’s suggestion of where argon gas would be placed; doboreiner’s grouping of elements amount the several steps that other scientists made were significant towards development of the modern periodic table. Also of greater importance is the accurate list of atomic masses of elements unveiled in 1860 at Karlsruhe, Germany. It made easy the arrangement pattern of elements since the data was made readily available. Therefore, the chronological order of events and how they developed reveals a linkage where one stage would build in to the other until Mendeleyev’s breakthrough. Reference Brewton-Parker College. (n.d.). History of the Development of the Periodic Table of Elements. Retrieved May 21, 2015, from http://www.bpc.edu/: http://www.bpc.edu/mathscience/chemistry/history_of_the_periodic_table.html Craig Freudenrich, P. (n.d.). Getting Organized: Origins of the Periodic Table. Retrieved May 21, 2015, from http://science.howstuffworks.com/: http://science.howstuffworks.com/periodic-table1.htm Royal Society of Chemistry. (n.d.). Development of the periodic table. Retrieved May 21, 2015, from rsc.org: http://www.rsc.org/periodic-table/history/about Scerri, E. R. (2006). The periodic table: its story and its significance. Oxford University Press. Scerri, E. R. (2011). The periodic table: A very short introduction. Oxford University Press. Western Oregon University. (n.d.). A BRIEF HISTORY OF THE DEVELOPMENT OF PERIODIC TABLE. Retrieved May 21, 2015, from www.wou.edu: https://www.wou.edu/las/physci/ch412/perhist.htm Read More