Chemistry

An Overview of the Periodic Table of the Elements



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The Periodic Table Explained





The periodic table is familiar to most people, but why was it created and what does it mean? If you have taken a chemistry class, you may be familiar with the periodic table and the elements contain therein. This research will provide the reader with a brief history of the origin of the periodic table and an explanation of why it is designed the way that it is.

Imagine having a collection of butterflies, how would you keep track of the different species, identify where they originated from, or recognize how many are the same color? Generally, you would classify and group the like butterflies in order to keep track. Well the periodic table is chemistry's method of categorizing and classifying similar elements. (Curran, 2008)

At first it may be necessary to learn how the table became known as The Periodic Table. Examining the organization of the table will show us that elements are arranged in a manner which is predictable and based on properties, periodically, thus the name Periodic Table. Over one hundred elements can be found on the table and they are listed in a sequence of seven rows and eighteen columns, the columns are classified as families and the rows are identified as a period. (National Science Digital Library, 2008)

The table was first created in 1817 by Johann Dobereiner, a German Chemist; he first noticed similarities between elements and their properties. He tagged is finding as a "triad" since it was mainly three elements in each group that had similar properties. An English Chemist John Newlands was responsible for the first update to the periodic table some fifty years after Dobereiner. Newlands identified that forty-nine well known elements would repeat the eight element when grouped by their atomic masses. Newlands coined his grouping of elements as "law of octaves" and arranged them in clusters of seven. (National Science Digital Library, 2008)

A third attempt at positioning the elements on the periodic table was done in 1860 by Lothar Meyer another German chemist. Lothar determined that if elements were grouped by their atomic mass particular properties would be repeated periodically. Shortly thereafter in 1869 a Russian Chemist Dimitri Mendeleev printed the first periodic table, leaving blank spaces for unknown elements while grouping the other elements into eight columns. His foresight was proven to be correct as other elements were later added to the table. (American Institute of Physics, 2008)

In 1914 after determining the atomic mass of numerous elements Henry Moseley corrected the periodic table. Thus the periodic tables as we know it today is structured so that the properties displayed are by the elements and they function based on their atomic numbers. (National Science Digital Library, 2008)

Let's look at the structure of the periodic table and try to understand what it means. The table identifies the atomic number and atomic mass of all the elements and is designed according to the nuclear charge. The rows are named period and by examining each element's period you can identify the energy level that the valence shell is located. The columns allow you to forecast the valence shell arrangement. The elements are placed on the table in order of lightest to heaviest while the elements in each column have similar properties. (American Institute of Physics, 2008)



The periodic table has undergone many changes and updates however; each Chemist had the same concept, that elements contained within the table should be grouped by their likeness to similar elements. The table contains valuable information regarding the one hundred and ten known elements and how they relate to one another.

References

American Institute of Physics. 2008. Marie Curie and the Science of Radioactivity: The Periodic Table of Elements. Retrieved June 4, 2008, from http://www.aip.org/history/curie/periodic.htm
Curran, G. 2008. Science Help Online Chemistry. Lesson 3-4: The Periodic Table. Retrieved June 4, 2008, from http://www.fordhamprep.org/gcurran/sho/sho/lessons/lesson34.htm
National Science Digital Library. 2008. Teachers Domain. Resource: Periodic Table of the Elements. Retrieved June 4, 2008, from http://www.teachersdomain.org/resources/phy03/sci/phys/matter/ptable/index.html

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