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Modern Periodic Table.

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Introduction

Chemistry Essay Modern Periodic Table 1 Gallium 1 Spectroscopy 2 UNILAC 3 Chemistry in the last 200 Years 3 Bibliography 4 Modern Periodic Table The modern periodic table has evolved over mainly the last 200 years; one of the first methods for arranging the elements was by atom weights. This was done by Johann D�bereiner, he also arranged the elements into triads, these were groups of three elements which had similar properties, and the two outside elements has an average atomic weight to that of the middle element. John Newlands in 1863 noticed another pattern with the elements which was that if they were ordered with increasing atomic weights every eight element had similar properties and subsequently called this the Octave Law. A Russian in 1869, Dimitri Mendeleev, was the first chemist to leave gaps for elements which had not yet been discovered; he also noticed patterns within the elements and predicted the properties of these undiscovered elements. Mendeleev' predictions were confirmed in 1875 by a French chemist called Paul Emile Lecoq de Boisbaudran, using the method of spectroscopy he discovered ...read more.

Middle

Another unusual physical properties is that its only one of three elements which has a melting points near room temperature, this means that gallium will melt in the palm of your hand. The last unusual property is chemical, in that it dissolves in both acids and bases; this characteristic is shared with aluminium (fig2). The appearance of Gallium, in its colour and feel would indicate that it's a metal (Fig3), also its high boiling point also indicates that it's a metal, however the fact that the melting point is so low would indicate that it's a non metal. Acid Alkali Fig 2 (D) Fig3 (E) Spectroscopy Spectroscopy is method used by chemists to detect elements. It was discovered in 1860, and was used to discover new elements in the periodic table at the time. An electric arc, excites electrons within an atom, by this the arc gives the electrons energy, this energy, which is in packets, is adsorbed by the electrons in the atom, and the electrons move to a higher energy level within the atom. ...read more.

Conclusion

The nuclei' of the elements fuse, as the high speed ions overcome the repulsion of nuclei. However this method is only successful to an extent, the elements which are produced usually only last a fraction of a second and therefore will never have a practical use. The process of making the elements gets harder as the element's atomic number increases, with an increasing atomic number the time taken to obtain an amount of the element, which is detectable, becomes longer. This technique also relies on the knowledge of known atoms, as for a specific element to be created the atom number of the elements which will be used to make it have to be known. The structure will determine how the nuclei fuse and how the final element will come out. Chemistry in the last 200 Years During the last 200 years chemists have discovered methods to detect elements and classify them in a logical and informative method, which shows patterns and allows chemists to predict the properties of unknown elements. Chemists have also created methods to create new elements which are not found naturally, these elements are critical in the need for information about chemistry. ...read more.

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