John Dalton was born in 1766. He was born into a modest family in Cumberland, England. He earned a living for most of his life as a school teacher and a public lecturer. After teaching 10 years at a boarding school in Kendal, he moved on to a teaching position in the city of Manchester. There he joined the Manchester Literary and Philosophical Society, which provided him with a stimulating intellectual environment and laboratory facilities. The first paper he delivered before the society was on color blindness, and died in 1844.
Dalton joined the Manchester Literary and Philosophical Society and immediately published his first book on Meteorological Observations and Essays.
In this way, Dalton was able to start working out a table of atomic weights based on the lightest element, hydrogen, having a value of 1. He used his ideas about the make up of gasses this way, "we may form an idea of this by supposing a vessel filled with small spherical leaden bullets among which a quantity of fine sand is poured. The balls are to the sand as the particles of bodies are with respect to the caloric; with this difference only, that the balls are supposed to touch each other, whereas the particles of bodies are not in contact, being retained at a small distance from each other by the caloric." (Dalton)
Dalton's thoughts on his research allowed him to develop his theory were All matter was made up of hard round particles, which he called 'atoms', and that each type of atom, or element, such as hydrogen, oxygen, nitrogen, etc., differed from the next only by its weight.
The atomic theory had been born....
But his next idea was one of equal genius, how to represent this idea symbolically so that tiny, invisible particles could be 'seen' and their combining properties studied.
The solution was that Dalton thought, was to draw circles, each circle representing one of his tiny atomic spheres. Each element could be notable by the contents of the circle.
Minggu, 06 September 2009
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