Slide 1

http://www.hobart.k12.in.us/ksms/PeriodicTable/mendeleev.htm http://russiapedia.rt.com/prominent-russians/science-and- technology/dmitry-mendeleev/ Slide 2 Slide 3 Slide 4 B = 11 Al = 27 ? = 68 Slide 5 C = 12 Si = 28 ? = 70 Slide 6 B = 11 Al = 27 ? = 68 C = 12 Si = 28 ? = 70 N = 14 P = 31 As = 75 Slide 7 B = 11 Al = 27 Ga = 68 C = 12 Si = 28 Ge = 70 N = 14 P = 32 As = 75 Slide 8 Slide 9 Table from Mendeleev's 1869 paper http://www.msnucleus.org/membership/htm l/jh/physical/periodictable/lesson5/periodic5 b.html Slide 10 Atomic Mass Atomic Mass Mendeleev and the Periodic Table Slide 11 B = 11 Al = 27 Ga = 68 C = 12 Si = 28 Ge = 70 N = 14 P = 32 As= 75 Slide 12 B = 11 Al = 27 ? = 68 C = 12 Si = 28 ? = 70 N = 14 P = 32 As= 75 Slide 13 Slide 14 Slide 15 Slide 16 Table from Mendeleev's 1869 paper http://www.msnucleus.org/membership/html/jh/p hysical/periodictable/lesson5/periodic5b.html Ga = 70 Ge = 73 Slide 17 Slide 18 Chemistry in 30 secs New Slide 19 Slide 20 Ge Slide 21 Mendeleev predicted the properties of aluminum, boron, and silicon. Gallium, scandium, and germanium were also found to fit his predictions. There were some discrepancies, but the format of the table is the basis of todays periodic table. Mendeleev also noted errors in the atomic weight of some elements. Mendeleevs table as published in 1869, had many gaps and questions. If you think it does not look like todays table, read the horizontal lines, and notice they are todays periodic tables Groups I-VIII. Slide 22 Slide 23 Slide 24 Russia marks the 175th anniversary of the founder of the Periodic Law of chemical elements, Dmitri Mendeleev. The periodic Law was discovered by the Great scientist in 1869 but has been amazing scientists and exerting influence on the development science across the world for 140 years. Dmitri Mendeleev made several discoveries and each discovery could bring him the honour of a scientist. However, the periodic system of chemical elements is undoubtedly in the first place. Many chemists at the time saw the links between elements but failed to systematize existing information and group the 60 elements, which were known accordingly, said vice president of the Russian Academy of Sciences, Academician Sergei Aldoshin. Dmitri Mendeleev could do this. Moreover, when he started to create the periodic system, suddenly he understood that beryllium spoils the picture and was on the beginning of the table and messed up all regularities. In these circumstances he made a bold move, of course. He took the third element and changed its atomic weight believing that it was determined inaccurately. Only a Great man, who believed strongly in what he suggests, could do such a move, said Sergei Aldoshin. After changing the atomic weight, all elements occupied their appropriated places. Then he even suggested that there should be two free cells for other elements adjacent to barium and aluminum. He named the two as ekabarium and ekaaluminum. Later there elements were discovered by foreign scientists. They are Scandium (ekabarium) and Gallium (ekaaluminum). The next stage of the study was to find the physical foundation of the periodic system, said Academician Aldoshin. Dmitri Mendeleev devoted the rest of his live to this area. He was aware that the reason here was not atomic weight. The system is based on the structure of the atom. Later Physic Moseley suggested that the number given to every element in the table by Mendeleev would play the basic role and this number is linked with the charge of nucleus. When the structure of the atom was studies it was become quite clear that the periodic system had been linked with the atomic structure, Academician Aldoshin said. The further progress in science confirmed that Mendeleev discovered a universal law. When the first artificial element was synthesized in the 40s the question was how to identify it and determine its properties. This could have been a difficult task if there was no periodic law, says head of the chemistry section of the department of chemistry and science of material of the RAN, Academician Boris Myasoedov. It has been proved that it is quite easy to determine the properties of an element proceeding from the periodicity. Presently, 118 elements have been discovered. And their properties are being determined proceeding from the periodicity of changes. By knowing the nuclear properties and electronic structure of one or the other element and structure of nucleus it is easy to determine its chemical properties. Under the regulations affirmed by the International Union of Pure and Applied Chemistry, to recognize the discovery of a new element there is a need to know its properties. In this case Mendeleevs Periodic Law is the lodestar. This is the main significance of the law to promote science, Academician Boris Myasoedov said. The scientific community at the time of Medeleev gave a cool reception to the discovery. They insisted that the law has no long-term prospects and it was incomprehensible what it should do for the progress of applied science. This was a reason why Mendeleev was refused to award the Academician status in 1880. Presently, scientists believe that from the standpoint of science this is the most fundamental and basic law. Its application is quite significant. The periodic Law has had a huge impact on the development of all disciplines of science, including chemistry, physics, geology and mineralogy. It is impossible to imagine the development of metallurgy with out it. This concerns the development of new structural materials for aviation and space technology. Academician Aldoshin said: When an element is subjected up to one million atmospheres and is heated up to tens of thousands of degrees Celsius, the objective laws stipulated by the periodic system might change. A study of all elements in their extreme conditions is another trend in the development of the Periodic System. Scientists response to the question, when the periodic table is completely filled is quite cautious believing philosophically that the knowledge of humanity is inexhaustible as the world surrounding it. They say about the possibility of discovering up to 150 elements. According to Dmitri Medeleev the periodic table will be filled and expanded in the future Slide 25 Mendeleev Slide 26 http://www.hobart.k12.in.us/ksms/PeriodicTable/mendeleev.htm http://russiapedia.rt.com/prominent-russians/science-and- technology/dmitry-mendeleev/ Slide 27