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The history of the periodic table

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Chemistry Open Book Paper: 2852 In this day in age we have the privilege to look at a structured periodic table, which displays all the known elements and substances that are on our universe. However it hasn't always been like that and over time the modern periodic table that we see today has developed. One of the ways in which the modern periodic table differs from earlier attempts to classify elements is that in 1817 a German scientist called Johann Dobereiner (left) tried to classify elements using their atomic mass then called atomic weights). Dobereiner was the first to attempt to classify elements. Dobereiner placed elements which had similar properties in sets of three which he called the law of triads. He realised that the middle element had properties that were an average of the other two members when ordered by the atomic weight. In 1863 the English chemist called John Newlands (right) published his version of the periodic table and proposed the Law of Octaves. Newlands recognised the fact that once the elements were written in order of increasing atomic weight every eighth elements has similar properties so therefore any given element will exhibit analogous behaviour to the eighth element following it in the table. ...read more.


This makes its use for high temperature thermometers. It has the longest liquid range of any metal and has a low vapour pressure even at high temperatures. The physical properties of gallium are considered to be unusual because the fact that is a solid at 298 K but melts only slightly above this temperature and it is this property suggests that is a metal. Another property that considers gallium to unusual is that it has a high boiling point of 2403�c and a low melting point. Another property of gallium that makes it unusual is that it shares with water the property of being denser as a liquid than as a solid from the top down. This suggestion can be applied to that of ice and water, and sets gallium apart as a non metal. Like aluminium the metal above it in the periodic table, gallium shares a lot of similar properties. A table to show the comparison of gallium to eka-aluminium. Eka-aluminium (Ea) Gallium (Ga) Atomic weight About 68 69.72 Density of solid 6.0 cm 5.904 g cm Melting point low 29.78 C Method of discovery Probably from its spectrum spectroscopically oxide Soluble in acid and alkalis Soluble in acid and alkalis chloride volatile volatile Like aluminium gallium reacts with hydrogen ions. ...read more.


This can determine what element it is and how it can be used and where it should go in the periodic table. The UNILAC accelerator can be to synthesise elements and compound. The nuclei of the elements can fuse together to make new elements. The way it is done is by firing ion at a rotating disc of the metal target. The new elements are separated and checked. The role of chemist plays a big part in everyday life. Over the past two hundred years their role has gradually increased. It started off with the discovery of elements. Then an appropriate way had to be devised for them to be classified hence the modern day periodic table that we now see. Then the search continued to discover new elements. More and more elements were found chemists, and scientist considered using it commercially, such as the manufacturing of food, health beauty products, fuels etc. The role of chemist have also become more important due to the fact that they can give an explanation of what is happening in our atmosphere, how it caused and how to reduce it e.g. global warming. Therefore the work and role of chemists is increasing and in becoming more valuable. Anthony Newton Anthony Newton Chemistry open book paper 2004 ...read more.

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