Atomic Weight Of An Element example essay topic

The History of the Periodic Table of Elements Dmitri Mendeleev and the early Periodic Table Dmitri Mendeleev was born in Tobolsk, Siberia, on February 7, 1834. He was the youngest of 14 children born to Maria Dmitrievna Korniliev and Ivan Pavlovich Mendeleev. His father was director of the local gymnasium. Maria Korniliev's family settled in Tobolsk in the early 1700's and introduced paper- and glass-making to Siberia. Unfortunately, Ivan died when Dmitri was quite young, leaving his wife to support the large family. The death hit them hard economically especially for a large family, which meant that Maria had no other choice but to find work.

Maria's family owned a glass factory and they allowed her to take over managing the company so she could support the family. Dmitri, being the youngest, appears to have been his mother's favourite child and was provided as many opportunities as she could afford. From his early years, she began to save money for Dmitri to attend the university. As he grew older, it became apparent that he had a bright future. At the age of 14, he was attending the Gymnasium in Tobolsk and his mother was continuing to plan for his future. In that year, however, a second major family tragedy occurred; the glass factory burned to the ground.

The family was devastated. Maria was not about to give up her dreams for her son. She knew at this point that Dmitri's only hope to go on to school was to win a scholarship. So in his final years at the gymnasium, Maria pushed Dmitri to improve his grades and prepare for entrance exams. After much nagging from his mother and Bessargin, Mendeleev passed his gymnasium exams and prepared to enter the university. In 1849 they moved Moscow.

At this point the family included Maria, Dmitri, and Elizabeth (Dmitri's older sister). In Moscow, they entered a climate of considerable political uproar, which made the university reluctant to admit anyone from outside of Moscow. Mendeleev was rejected. Maria did not give up, however, and the family headed for St. Petersburg. Mendeleev was left alone to face his work at the university. Dmitri fell right into his work at St. Petersburg.

Mendeleev graduated and was awarded the medal of excellence for being first in his class. Mendeleev already had his life's ambitions in mind and, hoping to extend his life as long as possible, he moved to Simferopol in the Crimean Peninsula near the Black Sea in 1855 as chief science master of the gymnasium. He was 21 years old. In 1856, Mendeleev returned to St. Petersburg and defended his master's thesis: 'Research and Theories on Expansion of Substances due to Heat.

' Following his masters program, Dmitri focused his life on his career of teaching and research. He was essentially a teacher devoted to his work. The first led to his books and the periodic table. In 1859, he was assigned by the Minister of Public Instruction to go abroad to study and develop scientific and technological innovations. Between 1859 and 1861 he studied the densities of gases with Renault in Paris and the workings of the spectroscope with Kirchhoff in Heidelberg. He also tested for the critical temperature.

While in Heidelberg he met A.P. Borodin, a chemist. In 1860 at the Chemical Congress at Karlsruhe, Mendeleev had the opportunity to hear Cannizzaro discuss his work on atomic weights. Following his trip abroad, the Russian chemist returned to his homeland where he settled down to a life of teaching and research in St. Petersburg. In 1863 he was named Professor of Chemistry at the Technological Institute and, in 1866, he became Professor of Chemistry at the University and was made Doctor of Science for his dissertation 'On the Combinations of Water with Alcohol'. As will be seen, his research findings were expansive and beneficial to the Russian people. Dmitri was always in touch with the classroom.

Much of his lab work, including that on the periodic chart, occurred in his spare time following his lectures. The Original Periodic Table. Reihe n Gruppe I. -R 2 O Gruppe II. -RO Gruppe.

-R 2 O 3 Gruppe IV. RH 4 RO 2 Gruppe V. RH 3 R 2 O 5 Gruppe VI. RH 2 RO 3 Gruppe VII. Di = 138? Ce = 140 - - - - - - - 9 (-) - - - - - - 10 - -? Er = 178?

La = 180 Ta = 182 W = 184 - Os = 195, Ir = 197, Pt = 198, Au = 199 11 (Au = 199) Hg = 200 Tl = 204 Pb = 207 Bi = 208 - - 12 - - - Th = 231 - U = 240 - - - - - Mendeleev was not afraid to express his political views: These thoughts led him to the discovery of the periodic law, among other things, but also led to his resignation from the University on August 17, 1890. His most famous publications include Organic Chemistry, which was published in 1861 when he was 27 years old. This book won the Domi dov Prize and put Mendeleev on the forefront of Russian chemical education. The first edition of Principles of Chemistry was printed in 1868. Both of these books are classroom texts. Besides his work on general chemical concepts as discussed earlier, Mendeleev spent much of his time working to improve technological advances of Russia.

Many of his research findings dealt with agricultural chemistry, oil refining, and mineral recovery. Dmitri was also one of the founding members of the Russian Chemical Society in 1868, and helped open the lines of communication between scientists in Europe and the United States. Mendeleev also pursued studies on the properties and behaviour of gases at high and low pressures, which led to his development of a very accurate differential barometer and further studies in meteorology. His greatest accomplishment, however, was the stating of the Periodic Law and the development of the Periodic Table. From early in his career, he felt that there was some type of order to the elements, and he spent more than thirteen years of his life collecting data and assembling the concept... Mendeleev was one of the first modern-day scientists in that he did not rely solely on his own work but rather was in correspondence with scientists around the world in order to receive data that they had collected.

He then used their data along with his own data to arrange the elements according to their properties. In 1866, Newlands published a relationship of the elements entitled the 'Law of Octaves'. Mendeleev's ideas were similar to those of Newlands but Dmitri had more data and felt that Newlands had not gone far enough in his research. By 1869, the Russian chemist had assembled detailed descriptions of more than 60 elements and, on March 6, 1869 a formal presentation was made to the Russian Chemical Society -'The Dependence Between the Properties of the Atomic Weights of the Elements.

' Unfortunately, Mendeleev was ill and his friend Professor Menshutken gave the presentation. There were the exact eight points to his presentation: 1. The elements, if arranged according to their atomic weights, exhibit an apparent periodicity of properties. 2. Elements, which are similar as regards their chemical properties, have atomic weights that are either of nearly the same value (e.g. Pt, Ir, Os) or which increase regularly (e.g. K, Ru, Cs). 3.

The arrangement of the elements, or of groups of elements in the order of their atomic weights, corresponds to their so-called valencies, as well as, to some extent, to their distinctive chemical properties; as is apparent among other series in that of Li, Be, Ba, C, N, O, and Sn. 4. The elements which are the most widely diffused have small atomic weights. 5. The magnitude of the atomic weight determines the character of the element, just as the magnitude of the molecule determines the character of a compound body. 6.

We must expect the discovery of many as yet unknown elements-for example, elements analogous to aluminium and silicon- whose atomic weight would be between 65 and 75.7. The atomic weight of an element may sometimes be amended by a knowledge of those of its contiguous elements. Thus the atomic weight of tellurium must lie between 123 and 126, and cannot be 128.8. Certain characteristic properties of elements can be foretold from their atomic weights. (18) On November 29, 1870, Mendeleev took his concept even further by stating that it was possible to predict the properties of undiscovered elements.

He then proceeded to make predictions for three new elements (aluminium, boron and silicon) and suggested several properties of each, including density, radii, and combining ratios with oxygen, among others. The science world was perplexed, and many scoffed at Mendeleev's predictions. It was not until November 1875, when the Frenchman Le coq de Boisbaudran discovered one of the predicted elements (aluminium), which he named Gallium that Dmitri's ideas were taken seriously. The other two elements were discovered later and their properties were found to be remarkably similar to those predicted by Mendeleev.

These discoveries, verifying his predictions and proving his law, took him to the top of the science world. He was 35 years old when the initial paper was presented Throughout the remainder of his life, Dmitri Mendeleev received numerous awards from various organizations including the Davy Medal from the Royal Society of England in 1882, the Copley Medal, the Society's highest award, in 1905, and honorary degrees from universities around the world. Following his resignation from the University of St. Petersburg, the Russian government in 1893 appointed him Director of the Bureau of Weights and Measures. This was believed to have been done to keep down public disapproval of the government. Mendeleev continued to be a popular social figure until his death, on January 20, 1907 at the age of 73 The set out of the Periodic Table There were some inconsistencies in the arrangement of the elements according to his law, however it wasn't until the early 1900's (1914) that a Prof Moseley, a British Physicist, was able to determine the atomic numbers of all the known elements using an experimental technique. Moseley then proceeded to rearrange the elements according to increasing atomic numbers.

Moseley's arrangement seemed to clear up the contradictions and inconsistencies of Mendeleev's arrangement, but Moseley based his arrangement on atomic numbers and not atomic masses. Moseley's periodic law is now considered the current Periodic Law. It resulted in a slight alteration of Mendeleev's arrangement, but the slight difference was enough to correct the inconsistencies that existed in Mendeleev's arrangement. The elements are arranged in vertical columns known as Groups. The elements in each group have consistently high or low values for certain properties. The horizontal rows of elements are referred to as 'periods' Group 1 is called the alkali metal group.

These are strong metals that are unusually soft and very reactive toward Oxygen forming Oxides and water forming hydroxides of the metal. These elements are so reactive toward Oxygen and water vapour that they are stored under an inert liquid to protect them from Oxygen and water vapour. Group 2 is called the alkaline earth metals. These metals are not as soft as Group 1 metals. They also react more mildly with Oxygen to produce oxides of the metals and only react with water at temperatures where the water is steam.

Groups 3-12 are referred to as the transition metal groups. These metals are not as predictable because of the shielding effect of the inner electrons. Groups 1-2 and 13-18 are referred to as the representative elements Group 17 is referred to as the halogen group Group 18 is referred to as the Noble gas group previously known as the inert gas group. There are two special series of elements that occur right after the transition metal element Actinium (Actinides) and Lanthanum (Lanthanides). The Modern Periodic Table The ideas of Mendeleev have led to huge developments in the Periodic Table. His principles on producing the table have made it easy to produce new versions of the table when new elements are discovered.

Discovery of Elements The table below (that was provided to me by chemical elements. com) shows the date of which the elements were discovered. Many elements have been known since the Ancient Civilisations (i.e. Sulphur, copper, Lead and Silver). Others such as Ununbium have been discovered in recent years (1996).