Mendeleev discovered the periodic table while attempting to organise the elements in February of 1869. He did so by writing the properties of the elements on pieces of card and arranging and rearranging them until he realised that, by putting them in order of increasing atomic weight, certain types of element regularly occurred. For example, a reactive non-metal was directly followed by a very reactive light metal and then a less reactive light metal. Initially, the table had similar elements in horizontal rows, but he soon changed them to fit in vertical columns, as we see today. Not only did Mendeleev arrange the elements in the correct way, but if an element appeared to be in the wrong place due to its atomic weight, he moved it to where it fitted with the pattern he had discovered.
In 1829 Alexandre-Emile Béguyer de Chancourtois organized the elements according to the increase of their atomic weight and arranged them in a spiral on a cylinder. Despite the arrangement of all known elements he could not have displayed them correctly because of the wrong calculations. Nevertheless, that was the earliest form of the periodic table (Figure 1). The first
Meyer & Mendeleev produced their Periodic Tables simultaneously. Dmitri Mendeleev 1869 Produced a table based on atomic weights but arranged 'periodically' with elements with similar properties under each other. Gaps were left for elements that were unknown at that time and their properties predicted (the elements were gallium, scandium and germanium). The order of elements was re-arranged if their properties dictated it, eg, tellerium is heavier than iodine but comes before it in the Periodic Table. Mendeleev's Periodic Table was important because it enabled the properties of elements to be predicted by means of the 'periodic law':
It not only disproved Thomson's atomic model but also paved the way for such discoveries as the atomic bomb and nuclear power. The atomic model he concluded after the findings of his Gold Foil experiment have yet to be disproven. The following paragraphs will explain the significance of the Gold Foil Experiment as well as how the experiment contradicted Thomson's atomis model. Rutherford began his experiment with the philosophy of trying "any dam fool experiment" on the chance it might work.1 With this in mind he set out to disprove the current atomic model. In 1909 he and his partner, Geiger, decided Ernest Marsden, a student of the University of Manchester, was ready for a real research project.2 This experiment's apparatus consisted of Polonium in a lead box emitting alpha particles towards a gold foil.
The position an element is in on the table allows a scientist to easily judge its properties, its reactivity and its similarities to other elements. Dmitri Mendeleev’s Periodic Table: Dmitri Mendeleev, a Russian scientist, is said to be the father of the periodic table. In 1947 Mendeleev, while working on a textbook, began to organise the 63 elements that were known at the time in groups that displayed similar properties. Mendeleev found it difficult to classify certain alkali metals and metals, and while trying to find a way to classify them he began to notice that the properties and atomic weights of halogens and alkali metals shared similar patterns. He then began to investigate extensions of these patterns within the other elements.
The book was published in 1794. He first stated his theory in 1803: that each chemical element is composed of its own kind of atoms, all with about the same weight. His theory explained why one substance with a curtain amount of mass joins with another substance with the same amount of mass, which forms compounds; this doesn't alway take place. His law also concluded that two solids can not occupy the same space at the same time, although he concluded that a liquid, and a gas can occupy the same space at the same time. His law was the first useful atomic theory of matter.
Neils Bohr’s model was based on his observations of the atomic emissions spectrum of the hydrogen atom (Coffey, Universe Today). His findings said that the electron can move to a higher-energy orbit by gaining an amount of energy equal to the difference in energy between the higher-energy orbit and the initial lower-energy orbit (pg.102, line 20). But time and research has proven and changed the Bohr model; Making this model one of the most famous models in Chemistry history. As stated earlier, Bohr said that electrons are at a set distance from the nucleus, but this proved to be true only in the hydrogen atom. Bohr’s model of the hydrogen atom explained /observed spectral lines so well that many scientists concluded that the model could be applied to all atoms (pg.103, line 8).
In order to fully understand how nuclear weapons work, it is crucial to first understand the basic atomic structure of an atom. The discovery and contribution of the atom formed the foundation of modern nuclear weapons. Along with that comes the generation of electricity through the use of nuclear power. A Greek dilettante by the name of Democritus was known to be the first to theorize the atom as the universal building blocks of all things during the fourth century B.C. He was amplifying an earlier notion by his mentor and philosopher Leucippus.
In 1921 the first edition was actually published by Ernest Bircher. The test appeared under the name of a book called Psychodiagnostik, which had actually been first written by Hermann Rorschach in 1919 but he had problems finding a publisher so it was not well received when it first came out. Since 1927 Hans Huber has been the publisher of the Rorschach test and the related book Psychodiagnostics (English ... ... middle of paper ... ...ut turning the cards at odd angles or covering portions of the cards is considered as signs of brain damage. In conclusion, even though the test was developed for purposes totally unrelated to accessing character structure and personality problems, psychologists today have found ways to use this test in order to help access personality and probe the unconscious mind. Also, despite all the controversy that is caused by this test regarding the results and if they are meaningless, there are still findings that even though throughout the decades it is used less, to this day it is still a number one choice to assess a personality.
Dimitri Mendeleev arranged 63 known elements, into the periodic table based on atomic mass and predicted the existence and properties of new elements. He realised that the physical and chemical properties of elements were related to their atomic mass and arranged them into groups of elements with similar properties. Where there were gaps he succeeded in finding the atomic masses and there properties and was later discovered to be right. He was very strict on the atomic weight order. In addition to this he invested the thermal expansion of liquids.