Weight Theories Of The Atom example essay topic

The notion of the atom all stared about 450 BC when a Greek scholar starting think when can something break on more, when are the pieces at their smallest, this mans name was Leucippus. Leucippus also had pupil who also thought the same way as Leucippus, his name was Democritus. They developed there ideas and when Democritus died his theory summed up briefly was that everything in the world was made of tiny pieced that could not be broken up any more. That how the word atom was derived from the Greek work "atoms" meaning "unbreakable".

This was the start of the theory of atoms. The first time this theory was taught at a school was by Epicurus 306 BC which he established himself. The theory laid dormant for about 2 millenniums this was basically because it was all but forgotten, this was because it had no evidence, and it was only logic. One of the first people to show some evidence was Robert Boyle, an English chemist.

In 1662 he conducted 'Boyle's experiment and compressed air in a 'J' tube with mercury, this opened up a whole new window. This lead to new and old thought about different types of atoms, elements. The Greeks thought similar to this but only divided it up into four groups. Their theory was close to Boyle's but Boyle had a more concise idea of these elements and by the end of the 1700's they had discovered about 30 elements. In 1972 Frenchman Antoine Laurent Lavoisier discover the no mater what happens a substance always has the same weight. In the late 1700's another Frenchman, Proust, discovert that elements can be combined to make different compounds, and that certain proportions had to be used.

This became know as "law of definite proportions". A few years later an English chemist, John Dalton, a fan of Boyle worked on Proust's theory and came up with "the law of multiple proportions". Dalton soon came up with 'weight' theories of the atom a discovered that hydrogen was the lightest. In 1813 Jons Jakob Berzelius created a system using the Latin words for the element to represent that element. In 1860 the chemist of Europe had their first international Chemical Congress to discuss the matter.

They theory that prevailed was Cannizzaro theory. John Thomson was born in 1856, and is recognised as the British scientist who discovered and identified the electron. In 1897 Thomson demonstrated that cathode rays - high-speed electrons emitted by a negative electrode of a vacuum tube when an electric current passes through it - were actually units of electrical current that were made up of negatively charged particles that were smaller than an atom. Rutherford was born in 1871 in New Zealand. In early 1915 he announced his version of an atom structure: a very small, very tightly packed, charged nucleus which had electrons orbiting it. Bohr was a Danish physicist who was born in 1885.

He thought that electrons move in definite orbits around the nucleus, like planets moving around the nucleus. Bohr proposed that each electron moves in a specific energy level and this is the theory that is currently used in today's world. But with the extra addition of Chadwick witch came in 1932 that there are also neutrons in the nucleus but they have no charge but weight the same as protons.

Bibliography

Book; Chemical Connections, Book One, By Maria James, 1991 Book; how we found out about atoms, by Isaac Asimov.