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How did Chemistry begin?

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Introduction

How did Chemistry begin? Alchemists The alchemists of the 16th and 17th century tried to change one substance into another for the society including changing 'base metals' such as lead into gold. They also discovered arsenic and zinc and others Robert Boyle Robert Boyle was the first to define an element. Priestly and Lavoisier Joseph Priestly was an English chemist - by collecting gas produced when mercury (II) oxide is decomposed by heating, and thus being the first person to isolate elemental oxygen. Antoine Lavoisier was investigating the oxidation of mercury in air. Lavoisier measured the mass of reactants and products in the reaction. He demonstrated that oxygen was the component of air responsible for the apparent increase in mass observed in combustion reactions. Lavoisier's contributed to the Law of Conservation of mass. Davy When the electrochemical cell had only just been invented, Davy began to experiment with electrolysis. Using a battery made from alternating zinc and copper plates in electrolyte solution, he extracted sodium and potassium metals from their molten salts in 1807. Davy has used electrolysis to discover Barium, calcium and strontium. ...read more.

Middle

Using periodic trends and chemical properties of elements next to gaps in his table, Mendeleev predicted the properties of undiscovered elements. He predicted germanium to be a density of 5.5 g/ml and a high melting temperature. When germanium was discovered it had density of 5.4g/ml and melting temp of 958 degrees. Discovery of noble gases The presence of relatively un-reactive gas, nitrogen and reactive gas, oxygen in air had been discovered. Henry Cavendish discovered that a spark through the air caused N --> N oxides, which could then be extracted by chemical reaction from the remaining gases. By adding more oxygen to sparked air, he tried to completely remove nitrogen gas. Whilst all the nitrogen could be removed, one percent would not react. He suggested that this might represent a new gas. Lord Rayleigh discovered that the density he measured for samples of nitrogen obtained from air was 1.257 g/l whereas 1.251 g/l for nitrogen produced by chemical reactions. He was assisted by William Ramsey who isolated the gas that remained when N and O were removed from air and examined the spectrum produced when it was heated. ...read more.

Conclusion

A new type of penetrating radiation had been discovered and it was quickly shown to be emanating from the uranium atoms. Marie Curie measured amount of radiation emitted by uranium, she and her husband Pierre found that uranium ore produced far more radiation than could be accounted for in terms of uranium content. They suspected the presence of an uncovered element much more radioactive than uranium. They processed the tonnes of uranium ore to extract a compound of the new element, which was named polonium. Despite the high radioactivity of polonium, Curies found that the presence of this in uranium still did not account for the levels of radioactivity measured for ore samples. The existence of another element was suspected. Curies managed to extract one gram of a new, more radioactive element. They called it radium. The elements polonium and radium are radioactive because their atoms are unstable and break down into smaller particles The source of polonium and radium is elements such as uranium which are continually breaking down in multi-step nuclear reactions to form lead. Polonium and radium are just two of the several elements formed during the course of this process and are therefore always present in uranium ores. ...read more.

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